Cheapest rail to send money right now

Live network fees for the three rails people actually use for small transfers, for a plain one-input two-output transaction. USDT on TRON is listed twice because the first transfer to an address costs double.

Why USDT on TRON costs what it costs

A TRC-20 transfer burns energy: about 65,000 for a recipient who already holds USDT and about 130,000 for one who never has. Energy is paid in TRX at the chain's current energy price unless the sender has staked TRX for energy or rented it. The bandwidth part (~345 bytes) is usually covered by the free daily allowance. That is why exchanges charge a flat 1 USDT and why a $2 tip in USDT makes little sense while the same tip in Litecoin costs under a cent.