USDT, TON, TRX, and ETH all work for buying Telegram Stars, but each carries its own network fee on top of the order — and that fee isn't fixed. USDT sent on the TRC-20 network tends to run lower than ETH, particularly on Ethereum's base layer, but TON and TRX often land somewhere in between, and all four shift with how busy their networks are at any given moment.
Card fees don't change from order to order, but they're folded into the price either way, out of sight. Fees for USDT, TON, TRX, or ETH sit visibly on top of the Stars price and swing with network conditions — visible isn't automatically cheaper, it's just easier to see what's actually being paid for.
TRC-20 USDT transfers typically carry a low fee, but so can TON and TRX; ETH fees are the most likely to fluctuate meaningfully depending on when the transaction goes through.
It can be a larger share of a small order than a large one, so it's worth checking, but for most purchases the difference between USDT, TON, TRX, and ETH fees is small relative to the Stars price itself.
Usually not — converting between assets to chase a slightly lower fee often costs more than the fee difference it's meant to avoid.