Based on the experience I got, there is actually no such thing as an airdrop campaign that requires participants to pay for any reason. because airdrop is the giving of gifts from crypto projects that are completely free. you better have to rethink.
You're right, airdrop is a gift. But this time some people decided they were ok to pay a little amount. Reason is Dfinity will be huge !
Why KYC is necessary, airdrop like this would usually end up in a scam.
what I know is that any genuine or non-fraudulent airdrop will not ask for money for any reason, and if it is true that if it asks for money it means that the airdrop is doing fraud.
most Airdrops that ask for rewards from participants for sending tokens are fraudulent airdrops that we should avoid
Guys i invite you to get some informations about Dfinity.