In general, true airdrops shouldn’t cost money – that is you shouldn’t send money to receive airdrop tokens. This doesn’t mean an airdrop can’t make you spend gas to interact with a smart contract, it just means true airdrops shouldn’t financially benefit from being sent crypto or fiat.
A gray area has started popping up – projects that are dirt cheap to redeem, but not technically free. Currently our definition of what classifies as an almost airdrop is something that costs less than the equivalent of ~$2 USD. This is an arbitrary definition we made up, so it may change over time. As always, it’s up to you whether you participate – do your own research (DYOR).
So far, all of these almost airdrops are triggered by a website that triggers a smart contract to receive the tokens, usually by sending .002 BNB (~$0.60 USD).