Minimum Purchase Sizes and Why Small Buys Cost More

Small purchases pay a worse effective rate than large ones, and the reason is arithmetic rather than policy.

The two kinds of cost

Proportional costs scale: a one per cent fee is one per cent at any size. Flat costs do not: a three dollar withdrawal fee is three dollars whether the purchase was twenty dollars or twenty thousand.

Every onramp charges some of each. The mix decides how badly a small purchase is treated.

The arithmetic at four sizes

On a flat two dollar processing charge plus a three dollar network fee, with a one and a half per cent spread:

Purchase	Flat costs	Proportional	Effective cost
$20	$5.00	$0.30	26.5%
$100	$5.00	$1.50	6.5%
$500	$5.00	$7.50	2.5%
$2,000	$5.00	$30.00	1.75%

The percentages are illustrative, but the shape is not. The first row is the reason small test purchases feel like a bad deal.

Why venues set minimums at all

Below a certain size the venue loses money on the transaction, and below a smaller size the network fee exceeds the purchase. Minimums exist to stop both.

A venue with a low minimum is not being generous if the flat fees make that minimum uneconomic for the buyer.

The test purchase exception

A small first purchase to check that a route works is worth its terrible effective rate. The cost is a fee; the alternative is discovering a problem with a meaningful amount in transit.

Treat it as a cost of verification rather than as an investment and the arithmetic stops mattering.

What reduces the damage

Leaving the balance at the venue rather than withdrawing, where the venue is one you would leave a balance with. That removes the network fee, which is the largest flat component on a small purchase.

A regulated venue for the first purchase makes that a reasonable choice rather than a risk.

Where it stops mattering

Above roughly five hundred dollars at typical retail pricing, flat costs fall below half a per cent and the comparison between venues becomes a comparison of spreads.

That is the point at which exchanges that publish their deposit limits and their fee schedules start to be worth comparing carefully, and an onramp with the fee shown before confirmation starts to pay for itself.