If your variable costs feel high, you are not imagining it. Unlike rent or your Shopify plan, variable costs scale one-for-one with volume: sell twice as much, pay twice as much. That is exactly why they quietly determine whether growth makes you richer or just busier.
This guide breaks down which costs are actually variable, walks a real per-order calculation, and shows the specific reasons the number creeps up. For the full picture of how these lines sit inside your income statement, see the ecommerce P&L guide.
What counts as a variable cost
A variable cost is any cost that moves with the number of units you sell. Fixed costs (your Shopify subscription, a designer's retainer, insurance) stay flat whether you sell one order or a thousand. Variable costs are the ones that repeat on every order.
For a small Shopify or print-on-demand store, the variable list is short but heavy:
- Product cost / COGS — the supplier's production charge (blank garment plus printing) for the specific units sold.
- Supplier shipping — what your fulfiller charges to ship each order to the customer.
- Payment processing fees — a percentage plus a fixed fee on every transaction.
- Packaging — poly mailers, inserts, tape.
- Per-order labor — hourly packing or support time that rises with order count.
- Returns and refunds — refunded orders, plus fees you do not get back.
Ad spend also scales with revenue, but it is not a variable cost in the accounting sense — it belongs in operating expenses, not cost of goods sold. Burying it in COGS inflates your gross margin and hides your real risk. If you want the flip side of this topic — a variable-cost number that looks suspiciously low — read why your variable costs might be low.
Why the number climbs: the real drivers
1. Product cost is the single biggest line
For most print-on-demand stores, the supplier's production charge is the largest variable cost by far — often a third or more of the selling price. It is fixed per unit but scales linearly with volume, so it is the first place a "high" total comes from. Every markup decision starts here.
2. Payment processing quietly compounds
Every card sale carries a processing fee. On Shopify Payments, online card payments on lower-tier plans are commonly quoted at around 2.9% plus 30¢ per transaction, with the rate falling on higher plans, according to A2X's breakdown of Shopify fees. That 30¢ fixed portion hurts most on low-ticket orders — on a $12 sale it is a bigger slice than on a $60 one.
There are two hidden ways this line grows. First, using an external gateway instead of Shopify Payments adds an extra Shopify transaction fee on top of the processor's cut, per the same A2X guide. Second, refunds do not return the original processing fee — so a refunded order still costs you that fee for zero revenue.
3. Returns and chargebacks are pure leakage
A refunded $32 order does not just cost you the sale — you eat the roughly $1.23 processing fee anyway, plus any production and shipping already spent. Chargebacks are worse: a customer dispute on Shopify Payments carries a $15 fee in the US, refunded only if you win the dispute, again per A2X. A handful of disputes a month is a real dent in a small store.
4. Shipping and packaging scale with weight
Supplier shipping and your own packaging repeat on every order. Heavier or bulkier packaging raises both carrier fees and, for some fulfillers, handling. This is the line most stores never re-examine after launch.
5. You are paying supplier sales tax you could avoid
Here is the leak most print-on-demand sellers miss. When Printify or Printful produces your order, you are buying goods for resale — which should be exempt from sales tax if you file a valid resale certificate. Without one, your supplier charges you sales tax on every production order, even though you already collect tax from your own customer. That is double tax on the same item.
You generally need a registered sales tax permit first, then submit the certificate to each supplier before ordering — Printful reviews it in about two business days and Printify in roughly three to five, per the Printful and Printify help centers. There are no retroactive refunds, so orders placed before approval keep the tax. Set it up on day one. (This is general information, not tax advice. Rules change and vary by situation — consult a licensed CPA or tax professional before acting.)
A worked example: where the money goes
Say you sell a t-shirt for $32. Here is one order, line by line. These figures are illustrative — plug in your own.
- Selling price: $32.00
- Production (blank + printing): −$12.00
- Supplier shipping (bundled in production charge): included above
- Payment processing (2.9% + 30¢): 32 × 0.029 = $0.93 + $0.30 = −$1.23
- Packaging: −$0.50
Variable cost total: 12.00 + 1.23 + 0.50 = $13.73, or about 43% of the $32 price. That leaves $18.27 in gross profit per order before any ads or overhead — a gross margin near 57%.
Now scale it. At 300 orders in a month:
- Net sales: roughly $8,830 after a few discounts and refunds
- Total variable costs (COGS + processing): about −$3,946
- Gross profit: about $4,884, a gross margin near 55%
That looks healthy — until ad spend enters. If you spend $3,000 on Meta and Google plus about $770 in subscriptions, tools, and owner pay, operating profit lands near $1,114, or roughly 13% of net sales. The product economics are strong; the thin margin comes from acquisition cost sitting on top of already-heavy variable costs. If ad costs rise 20%, that $1,114 nearly halves.
The lesson: "high" variable costs are not automatically a problem — a 55% gross margin is fine. They become a problem when they leave too little cushion to absorb the ad spend on top. That is why per-order profit, not gross revenue, is the number to watch.
How to bring variable costs down
You cannot manage what you do not measure per order. Once you know the real per-order number, the moves are concrete: negotiate or switch suppliers on the production line, raise average order value so the fixed 30¢ fee shrinks as a percentage, keep payments on Shopify Payments to dodge the extra gateway fee, right-size packaging, and file that resale certificate. For a deeper playbook, see how to improve your variable costs, and to get the bookkeeping structure right underneath it all, the P&L accounting basics.
One caution: variable costs and cash timing are different problems. You can have healthy margins and still run short, because ad spend leaves your account daily while Shopify payouts settle on a delay. Cutting variable cost helps profit; it does not fix the float gap.
Where PodVector fits
The hard part is not the theory — it is knowing your true per-order profit when production charges, shipping, processing fees, and ad cost all live in different tools. PodVector connects Shopify, Meta Ads, Google Ads, Printify, and Printful, then computes true per-order profit so the variable-cost drivers above stop hiding inside a blended revenue number.
Victor, its AI employee, analyzes that live data and can act on it Shopify-side with your approval — flagging which SKUs carry the heaviest variable cost and where margin is leaking. Victor is not a dashboard, and he does not touch your ad account; he reads ad data and proposes moves, executing writes only on Shopify. If tax lines are part of your leak, the VAT calculation and reporting tools guide is the next stop.
See your true per-order profit with PodVector
FAQs
Why are my variable costs so high on print-on-demand?
Because print-on-demand has no economies of scale on production — you pay the supplier's full per-unit charge on every single order, plus their shipping. Unlike buying inventory in bulk, there is no volume discount baked in, so production alone often runs a third or more of your selling price. Add processing and packaging and half your revenue can be gone before ads.
Is payment processing a variable or fixed cost?
Variable. It fires on every transaction — a percentage plus a fixed per-transaction fee, commonly around 2.9% plus 30¢ on Shopify Payments for lower-tier plans, according to A2X. The fixed 30¢ portion makes it proportionally more painful on low-ticket orders.
Should ad spend count as a variable cost?
It scales with revenue, but in accounting terms it belongs in operating expenses, not cost of goods sold. Keeping it out of COGS is important: bury it there and your gross margin looks inflated while your real risk — customer acquisition cost — disappears from view.
Do refunds increase my variable costs?
Yes, in two ways. You lose any production and shipping already spent, and the original payment processing fee is generally not returned when you refund a customer. A refunded order can cost you a dollar or more in fees for zero revenue, so a high return rate quietly raises your effective per-order cost.
How do I lower variable costs without hurting quality?
Attack the biggest line first — usually production — by negotiating with your supplier or comparing fulfillers. Then raise average order value so fixed fees shrink as a share of each sale, keep payments on Shopify Payments to avoid extra gateway charges, right-size packaging, and file a resale certificate so you stop paying supplier sales tax. Measure per order so you know which move actually moved the number.
This is general information, not tax advice. Rules change and vary by situation — consult a licensed CPA or tax professional before acting.