Variable costs are the expenses that rise and fall with your sales volume. Sell one more shirt and you pay for one more blank, one more print, one more round of payment fees. Sell nothing and those costs go to zero.
Most articles on this topic stop at "negotiate with suppliers" and "cut waste." That advice is fine, but it never shows you the math. This guide does — with worked examples so you can see exactly where a dollar goes and which lever pays you back the most.
What counts as a variable cost (and what doesn't)
A variable cost scales with each unit you sell. A fixed cost stays roughly the same whether you sell ten orders or ten thousand.
In an online store, the classic variable costs are the direct cost of goods (COGS), payment processing fees, per-order shipping and packaging, and paid acquisition. Your Shopify plan, apps, insurance, and design tools are fixed — they belong in operating expenses, not in the cost of a single sale. If you want the full line-by-line layout, the ecommerce P&L guide walks through where every cost sits.
Getting this split right matters. If you bury ad spend inside COGS, your gross margin looks fat and you never notice that customer acquisition is quietly eating your profit.
Step 1: Measure your true variable cost per order
You cannot improve what you have not measured. So start with one order and add up every cost that moved because that order happened.
Say you sell a print-on-demand t-shirt for $32. The variable costs on that single order might look like this:
- Supplier production (blank garment plus printing): $12.00
- Payment processing (a common online card rate is around 2.9% plus 30¢ per transaction, per A2X's breakdown of Shopify fees): $0.93 + $0.30 = $1.23
- Extra packaging insert: $0.40
Add those up: $12.00 + $1.23 + $0.40 = $13.63 in direct variable cost. That leaves $32.00 − $13.63 = $18.37 of contribution before you spend a cent on ads.
Now bring in acquisition. If it costs you $10 in ad spend to win that order, your real contribution per order is $18.37 − $10.00 = $8.37. That $8.37 — not the $18.37 — is the number that has to cover your fixed costs and leave a profit.
Step 2: Pull the levers in order of size
Once you can see the parts, improve the biggest ones first. In the example above, the ranking is clear: production ($12), acquisition ($10), then fees and packaging. Spending an afternoon shaving pennies off packaging while ignoring a $12 COGS line is effort in the wrong place.
Cut cost of goods sold
COGS is usually the largest per-unit variable cost, so it is the highest-leverage place to start. Three moves work:
Negotiate volume pricing or switch to a cheaper supplier for the same quality. Say you move production from $12.00 to $10.50 per unit — a $1.50 cut. Across 300 orders a month that is 300 × $1.50 = $450 back in your pocket, every month, with no extra sales required.
Redesign the product to cost less to make: fewer print locations, a lighter blank, or standardized sizing that qualifies for better tiers. And submit a valid resale certificate to your supplier so you are not paying sales tax on the goods you buy to resell — Printify's resale certificate guide explains that without one, suppliers charge you tax on every production order. The P&L accounting breakdown shows how these direct costs flow through your gross margin.
Trim payment processing and fees
Processing fees are small per order but relentless — you pay them on every single sale, and refunds usually don't return the original fee to you.
The cleanest fix is to avoid stacking gateways. If you run an external processor on top of Shopify, Shopify adds an extra transaction fee that using Shopify Payments avoids, as A2X notes. Also watch chargebacks: Shopify Payments charges a $15 US dispute fee that is refunded only if you win, per the same source. Cutting your dispute rate is a real variable-cost win.
Reduce shipping and packaging
Shipping is often bundled into your POD supplier's production charge, so the lever here is choosing products and suppliers with cheaper or included fulfillment. Where you pack yourself, right-size the mailer and buy packaging in bulk.
Even a $0.40 packaging insert costs you 300 × $0.40 = $120 a month at 300 orders. Small numbers still compound.
Treat ad spend as your most important variable cost
For an ad-driven store, paid acquisition is often the second-largest variable cost and the one with the most room to move. Improving it usually means lowering cost per acquisition (CAC), not just spending less.
Say better creative and a tighter landing page lift your conversion rate so CAC drops from $10 to $7 per order. That $3 improvement flows straight to contribution: your per-order profit jumps from $8.37 to $11.37 — a 36% gain, before you change anything about the product. Because ad spend leaves your account daily while payouts arrive on a delay, it also strains cash; the ecommerce P&L guide covers that float problem in depth.
Step 3: Reprice or retire the orders that never clear
Not every product deserves the same effort. Once you know contribution per order, you can see which SKUs actually make money.
If a design nets $8 of contribution and another nets $2 after the same ad spend, you have three choices on the weak one: raise its price, cut its production cost, or stop selling it. Repricing is the fastest lever — a $32 shirt moved to $35 adds $3 of contribution per order with zero extra cost, as long as demand holds.
To decide, you need clean numbers per product, not blended averages. A structured ecommerce P&L template gives you a place to model each SKU before you touch prices.
Watch the profit angle, not just the cost
Here is the trap the generic guides miss: the goal of improving variable costs is not the lowest possible cost. It is the widest contribution margin per order.
You can cut COGS by switching to a flimsy blank and gain a dollar — then lose three dollars to returns and disputes. You can slash ad spend and watch orders disappear. Every variable-cost move has to be judged by its effect on per-order profit, not the cost line alone.
That is why the two most useful habits are booking every cost on the right line and knowing your true profit on each order. If your books lump the Shopify payout in as "revenue," you will never see your fees clearly — solid ecommerce bookkeeping fixes that, and clean books also make tax time defensible, which the seller taxes and income reporting guide explains.
This is exactly the problem PodVector was built for. It connects Shopify, Meta Ads, Google Ads, Printify, and Printful, then computes your true per-order profit — production, fees, shipping, and ad spend netted against what each customer actually paid. Victor, its AI operator, reads that live data, flags where your variable costs are quietly eating margin, and proposes moves (executing approved changes on the Shopify side; Victor does not touch your ad account). If you want to see your real contribution per order instead of guessing, try PodVector.
This is general information, not tax advice. Rules change and vary by situation — consult a licensed CPA or tax professional before acting.
FAQs
What is the difference between improving and simply cutting variable costs?
Cutting means spending less; improving means widening the gap between what you charge and what an order costs you. Sometimes that gap grows by lowering a cost, and sometimes it grows by raising a price or spending on ads that convert better. Judge every change by its effect on contribution per order, not by the cost line in isolation.
Which variable cost should I attack first?
Start with the largest one per order, which for most stores is cost of goods sold or paid acquisition. A dollar saved on a $12 production cost matters far more than a dollar chased on a 40-cent packaging insert. Measure your per-order costs first, rank them, then work top-down.
Is ad spend a variable cost or an operating expense?
It behaves like a variable cost because it scales with the sales you chase, but on the profit and loss statement it belongs in operating expenses, below gross profit. Keeping it out of COGS is what lets you see your true product margin and your acquisition cost separately. Blending the two hides which one is actually hurting you.
How do I know if a variable-cost change actually helped?
Compare contribution per order before and after the change, holding everything else steady. If production dropped $1.50 but returns rose and ate $2.00, the move lost money despite the lower cost line. This only works if your books record each cost on its own line and reconcile to your payouts.
Do payment processing fees really matter if they are small?
Yes, because you pay them on every order and refunds usually don't return the original fee. A rate of around 2.9% plus 30¢ per transaction, per A2X, is a few percent of revenue that compounds across thousands of orders a year. Avoiding stacked gateways and cutting your dispute rate are the two cleanest wins.