The seller still gets paid as long as the sponsor is able to sell it to someone else. In fact, the seller may even earn more than if they had not had a sponsor!
The seller chooses whether or not to allow buyers to sponsor and sets a time limit up to 60 days after the original sale. There is no limit to how many times a listing can be sponsored within the time limit set by the original seller, and the original seller receives 5% of every sponsored sale.
That means it is very possible to earn over 100% of the final sales price over the course of time people are sponsoring the seller’s listing!