I tried THORswap, they charge you $20 fee. So much for their advertisement of having native BTC.
If you're using Ethereum, then you're being charged Ethereum transaction fees (which are pretty high). You're going to get that high of a fee regardless of what smart contract you're going to use.
And yes, that is actually native BTC and not wrapped BTC(wBTC) because the funds get sent to an actual bitcoin wallet.