good question, I'll try to give an answer. Base is L2 blockchain, so the gas is really low (0.002$) you can see all the transactions from the tournament, they're 298. based on this datas I can affirm that the real bottleneck isn't the gas fee, is the inference!

forgot to mention: the facilitator pays the gas using EIP-3009. the result is that the USDCs go direct from buyer to seller.