While Santa has
slave labour the elves to make the toys, the toys have to be made from source materials, most of which may not be available on the North Pole.
So how does Santa actually afford the raw materials required to make the toys?
Santa is hundreds of years old (at least), is our world's first and therefore greatest expert on the delivery of items to people's houses, and he only works at his official gig for one day per year.
In his free time, he has parleyed that time and expertise, creating several commercial ventures which he secretly owns majority stakes in. Those ventures include... Fedex, UPS, and DHL.
Santa is a secret Billionaire!