I don't know if I'm using the correct swap or if this is something else, and I couldn't see an option for XMR to BTC. When I try to swap BNB to BTC, there's an $8 fee I think that's reasonable for dex, but we lose privacy here, which is a deal breaker for me. The Exch.cx was centralized, but they still kept privacy intact.
The fee depends on which affiliate’s frontend you’re using. From what I could find, Rango.Exchange has the lowest affiliate fee if you use their website directly instead of going through a wallet integration.
There isn’t currently an AMM DEX that supports Monero, but Luke Parker is working on SeraiDEX.