What is the cheapest way to exchange tokens (ETH/BSC/POLYGON) for Bitcoin?
(1) P2P, preferably your friend. You can hand him your private key, and he can give you his private key (barter). However, there will be problems if one side or both store backups. It's the cheapest, but not feasible in most cases.
(2) The 2nd cheapest for small amount is to use instant exchange such as changenow, changelly, etc., but it has a bad reputation on this forum.
(3) The 3rd cheapest is to use centralized exchange the likes of Binance et al.
For (2) & (3) you do it when the gas price is low.
Your chances are very low to exchange tokens for Bitcoin. The third one is the best options: " centralize exchange". But now Bitcoin investment isn't profitable. Why does someone want to exchange tokens for Bitcoin? We have one option if our tokens are ERC-20. It doesn't cost us the same 24 hours as you can see. GWEI is always changing if you check gas prices.