Don't Ignore E-Commerce Fees: How a 3% Platform Cut Eats Your Profit

The QuickCosting Team

A 3% fee sounds almost harmless. But when it's calculated on your selling price it quietly chips away at the profit you worked to build in. This is one of the most common oversights made and it's worth running the actual numbers.

The Setup: A Simple Product With a Clear Profit Target

Let's say you make a product with the following numbers:

  • Unit cost: 5
  • Desired profit per unit:
5
  • Selling price: $60

    • Example figures: Unit cost 5 | Target profit

    5 | Selling price $60

    For 100 units, here's what you expect:

    Per Unit 100 Units
    Revenue $60.00 $6,000.00
    Unit Cost 5.00 ,500.00
    Expected profit 5.00 ,500.00

    Clean. Simple. Now add the platform fee.

    What a 3% E-Commerce Fee Actually Costs You

    Most e-commerce platforms charge a percentage of the selling price. At 3%, that's

    .80 per unit on a $60 sale.

    That might sound minor. Here's what it looks like across 100 units:

    Per Unit 100 Units
    Revenue $60.00 $6,000.00
    Cost of goods 5.00 ,500.00
    Platform fee (3% of $60)
    .80
    80.00
    Actual profit 3.20 ,320.00

    You just lost

    80 in your desired profit without changing a single thing about how you make or sell your product. That's money you earned and then handed straight to the platform.

    And

    80 is just at 3%. Many platforms stack fees: listing fees, transaction fees, payment processing fees. It adds up fast.

    Why This Fee Gets Ignored

    There are two reasons sellers overlook platform fees:

    1. The percentage looks small. 3% feels like a rounding error. It's not, it compounds across every single sale.
    2. It's not part of making the product. Most people think carefully about materials, labor, and shipping. Selling costs feel like an afterthought or like something that happens after the real work is done.

    But selling expenses are a real cost of doing business. If you sell through a platform, that fee is as real as the materials in your product.

    Always Include Selling Fees in Your Cost Calculations

    The fix is straightforward: treat platform fees as a line item in your cost structure before you set your price, not after.

    If you need

    5 in profit per unit and your cost is 5, and you sell on a platform that charges 3%:

    5 (profit) + platform fee
  • Platform fee = 3% of your selling price
  • So: Selling price = $61.86

    • Round to $61.99 or $62.00, and now your fee is covered and your

    5 profit target is protected.

    This small adjustment of building the fee into the price from the start is the difference between hitting your margin and silently falling short of it.

    Platform fees aren't going away, and they're not negotiable. What is in your control is whether you account for them before you price, or discover them after you've already sold. Keep every selling expense in your cost calculations, every time, no matter how small the percentage looks on paper.