Is it possible to transfer money from one Apple ID to another?

You can send money from one appleid to another via Apple Pay, but if you're asking how to transfer store credit on iTunes (As in credit you get from iTunes gift cards and such), as far as I know that can't be done.

Send, receive, and request money with Apple Pay - Apple Support

(This is if you wanted to send money via Apple Pay, but I'm not sure if this is what you're looking for.)

No. However if you have redeemed a gift card to your account without using it then it may be possible to transfer the balance back to the gift card (with the assistance of iTunes Store support) and give that to someone else.

tt2