There is no shortcut to send tokens to a lot addresses other than using the normal ERC-20 functions. Therefore, airdropping tokens requires looping through all address/# token combinations and depending on how many you are sending to, can be expensive from a smart contract perspective. Without getting too technical this is the reason why gas can be quite high compared to other transactions you typically do on the blockchain, but for more information feel free to reach out and we can have a more technical chat.