Kari,
Items which are recieved from mission rewards are sometimes not correctly pulling their sell value. This is a known issue, but rewards should drop consistently enough that you should still be able to sell it and not loose too much money in the long run, so go ahead and sell it as you find it! :)

Lisa, I occasionally get my wizard items but also get a lot of ranger items and warrior items. So I think I only have about 5 equipped items for my class. Anyway, someone told me to try to do a sort on my items and then try to sell them and that worked to be able to sell them for the right $ amount instead of just one gold. It may work for you to be able to sell them at all? When you're in your inventory just click on the "sort" button at the bottom and then try to sell and see what happens.