CustomPapers would be surprised too. They don't have set rates, but their writers bid on projects; some may bid as low as $10, others as high as $20-$40. It's up to the writer how much they want to complete an available project for.
I know from experience that I never go $20-30 per page, and that for this 12 page paper it would be more like $120 at most. Of course any place that has bidding like that is hard for writers to make much money.
I will say that I never got cheated by custompapers, and that was the only company that didn't rip me off. Just don't expect to get rich working there.