maybe If you or all of us have BEP20 USDT network you will be billed in BEP20 BNB onwards. Based on that, to answer your question, BNB or USDT based on BEP20/BEP2 is cheap to exchange. I hope someone will correct me if I'm wrong, but this answer is based on my knowledge.

if anything, the fees will be much lower than those built on the Ethereum (ETH) blockchain and you can compare the fees to the Binance coin (BNB) in BC which should be the same.

On Binance Smart Chain (BEP20), the fees are much lower, BNB and USDT are both on BSC, the fees are also low and should be the same. but it also has to be seen from the network that you use in the market, namely GAS. so from here we can determine whether you are using the ETH or BNB network. if you use an eth-based network, of course, judging from the GWEI at that time, it can be expensive and it can also be cheap. and if you go through BNB it's usually lower