To be cheaper is not enough to be a good project. BNB is cheaper because no one is using it
Not only because of that. They use Tendermint consensus for Binance Chain and PoSA for Binance smart chain. This allows them to process transactions in more effective way.
But any chain which depends too much on support from one exchange is less trustable than Bitcoin or Ethereum.
TRON has a good balance between TPS capacity and decentralization.