Like opensea? While it is a marketplace for NFTs, the fee is certainly a big concern but it seems that most of the networks for altcoins aren't that expensive at all. But a time when the demand gets higher especially in the ERC20, the fees are also going to increase together with the demand.
Whilst there are other networks that are being supported for each coin, you can consider that as well that your marketplace is open for different networks and wherever is the customer is confident without having interruption and problems with the fees.