It's called Steam Wallet.
If he buys the collection for me and create a Steam account, I can pay him back with the money I have. Which is on Steam Wallet. Since I don't have international credit card, I can at least sell goods for people, so called hats and cards.
And once he gets it on Steam, it stays there... for buying more games or game cosmetics. At least he can add money to the Wallet directly, different than me.