The Real Cost
The price on a listing is not the cost of the order. The cost is the price, plus the network fee, plus the platform fee, plus the time you spend verifying and waiting, plus the mistakes that are not on any invoice. Here is the full accounting, because the last line is the one people forget.
The fees you can see
The network fee is the chain charging for the transaction, and it varies by coin and by congestion. The platform fee is flat, published, and applied on withdrawal. Together they are small on a normal order, closer to the network fee alone than to a percentage of the total. That part of the cost is the boring part, and it is the part you can plan for.
The time you spend
Verifying an address takes two minutes. Waiting on a dead drop takes days. Reading feedback takes a few more. The time is a real cost, and it is the one that scales with how careful you are. The careful buyer spends more time per order and has fewer bad orders, which is a trade most people make without naming it.
The mistakes not on the invoice
A deposit to a lookalike. A balance held too long. A mnemonic stored in the wrong place. None of these appear as a fee, and all of them cost more than every fee combined. The real cost of the darknet is not the price tag. It is the part of the process that is on you, and the part you skip is the part that bills you.