yup, shutterstock retains tax from sales in the US. In a way that is paying fee too i guess but shutterstock somehow promotes your portfolio and sales everytime you upload a batch (reasonable number not just 1 or 2) of photos that get approved
I think Shutterstock is one of the fastest selling site in terms of volume together with iStock, but Dreamstime is one of the better paying ones in terms of pay image earnings