Indeed the true meaning of airdrop is any token to be given for free without any investment and airdrops are part of the allocations of every newly develop projects but its totally different once it is asking you to give any amount just to claim it, I think its a red-flag as indication of airdrop but instead its a fraud or scam airdrop.
What you said is true because in general the Airdrop is free and you don't have to give anything to get it, only in general the rewards from the Airdrop are mostly very small and the value is very low, although not all Airdrops are as I said, but most of them are like that.