A lot of depends from the project. Now gaming NFT projects attract a lot of attention and their airdrops are very popular. Just see the results of this airdrop
https://twitter.com/spacegrime/status/1396545308809601025 and you can see how popular gaming airdrops and how many users they have.
Now NFT are given on airdrops to attract attention of the cryptocommunity to the project. But the price of NFT depends on the demand in it and how many users want to buy NFT. It must be competition between buyers who want to buy NFT.
NFT airdrops attract a lot of people to the NFT projects. You can see how many people participate in NFT airdrops and how popular are they. Now a lot of people earn money on NFT and a lot of people want to participate in airdrops.