Yeah also in my opinion it stop being an airdrop when you put a condition of purchase token to get certain amount as free, airdrop should be given without condition to buy so more people will be curious and want to know more about project,

this is the way i come to know about trx, because of binance airdrop in my wallet, then i make research on trx and make my decision to invest on it. Thats how you draw attention. I miss my opportunity to buy on ripple, i will be researching on this though. Good luck.