No cost for everything.

If you're talking about IG money (galleons, sickles and knuts), I don't really get what the issue is, you receive 500G at the beginning of your adventure and it is well, realistic, that you have to spend a lot of it in order to buy items and register to classes. Then it is your choice to buy other items, and you have to manage your Gringotts account wisely. 

If you're talking about real life money (dollars, euros), it is never mandatory to buy VIP or anything else that requires IRL money. So I don't understant the issue here either...