lightning is a pain to set up, you have to open a channel and keep funding it - so if we are talking about small amounts these costs should definitely be added to your calculation. or you use lightning via an exchange - but that again kinda defeats the purpose of bitcoin. in fact all of this could probably be achieved much simpler by just using a stablecoin on tron, solana or one of the ether chains and forget about the whole lightning sending and bitcoin hedging. I doubt you can get lower transaction costs end-to-end staying on btc.