I want to say first, airdrop is free. The bull market will start in 2025, and most telegram mini games are currently running. Although few projects are paying off so far. OP As you say many projects are asked to do ton transactions. Yes, it is true that they ask for transaction in almost all free projects, but it is not mandatory. If you feel like it you will, and if you don't want to don't. I think no money should be spent on freebies. If you spend money on it, you get some more rewards.
just be sure to filter out for those grifter project asking 0.5 TON or more to finish the task though, most of the freebies project despite also have optional task to do TON transaction still put boundary where they only require a transaction and not require the money.
but if they demand the money however, big fat chance they just trying to profit off people. so I don't think that's a good project, but since it's optional anyway, just don't finish this one task only to avoid getting milked by the devs then things will be fine.