The miyata has the most value out of the lot and the Trek should come in 2d. Vintage MTBs generally aren't worth a lot. I'd value the MTB around a $100 fixed up and ready to ride. The miyata 610 has some value as used touring bikes tend to hold their value well. $250-$300 for the miyata fixed up and ready to ride; $200-$250 for the Trek.

Mixes are hard to value. They tend to sell well in large cities and university towns.