What would a full set of Tempest in NM condition go for?

Little back story. There is a sports card store near my house. Only play in town that sells singles. Not the best selection of magic cards and everything is overpriced probably because he mostly deals in sports cards. Lately I have been going there a couple times a week to look though his thousands and thousands of cards. Today we were talking and he asked if I could price a couple cards for him. At the end of the night he pulls out a box with the full set of tempest badlands and all. I did some quick math and came up with 650$ on the high end. What would be a good price to try and sell them at?