According to the latest data from BitInfoCharts, the average transaction fee for Ethereum (ERC20) is $9.65, for Binance Smart Chain (BEP20) is $0.15, and for TRON (TRC20) is $0.01. Therefore, based on these numbers, TRC20 is the cheapest option to send USDT to an address, followed by BEP20 and then ERC20.

However, these numbers are subject to change depending on the network conditions and the gas price you choose. Therefore, you should always check the current network fees before sending any transaction. You can use tools like GasNow for Ethereum, [BSCScan] for Binance Smart Chain, and [TRONScan] for TRON to monitor the network fees and gas prices.

I hope this helps you. Have a nice day! 😊