At least here in Australia, Steam vouchers get sold in supermarkets and any one at any age can buy them. I'm not sure if those vouchers work on the Steam market

At least here in Australia, Steam vouchers get sold in supermarkets and any one at any age can buy them. I'm not sure if those vouchers work on the Steam market but I'd assume they would (I've never seen anything in the Steam UI to suggest that deposited funds will only work in some places).