Every write to this contract is a regular Soroban transaction and
pays the network's standard resource fee — there is no separate
"platform fee" charged by the contract itself. The only value the
contract ever moves beyond the caller's own transaction fee is the
payment_token amounts in purchase_primary and buy_resale
(primary sale proceeds and resale royalty/seller proceeds).
Callers should simulate before submitting (simulateTransaction /
prepareTransaction in the SDK) to get an accurate resource fee for
the specific operation, since fees scale with the footprint touched —
issue_ticket and buy_resale touch more storage than a simple
verify_ticket read.