That's not airdrop anymore if there's minimum deposit involve since we can call that as investment. People should avoid to get fooled in that schemes since this action is usually made up by scammers. If they are interested with airdrops they should participate on legitimate programs which doesn't required their money especially their private key. This scheme is not new and there's a lot of post or articles posted to warn people regarding on this methods used by scammers so hopefully they take time to research before participating on anything they are not familiar.
Legitimate airdrops only require people to do some task for them and no other thing that can cause people harm. If they found out that the one they see is risky, better leave so they could able to save their money and effort on those scams.