Matt Moser (ForFruitTrees.com - Moser Fruit Tree Sales)sells fruit trees for most of the major growers in the country, and if you are in need of 25 or more trees, he's the guy you need to talk to.
Last spring ('07), I needed about 35 trees from 4 different nurseries that were on opposite sides of the country. By going through Moser's, I was able to buy them without paying an average of $20.00+ dollars per tree that they would have cost by buying small quantities from the different nurseries. He purchases them in large volume, and even after paying him to deliver them to the East side of Michigan, they still were less than $10.00 per tree.
He can get you any variety, rootstock, and caliper that is available, and if you're not sure what you need, he can help with what's best for your area.
Moser's is an excellent company to deal with, and anyone from a beginner to a pro will be happy with their service and knowledge.
They also sell trees in smaller volumes, and even though they cost more, they are still less than most mail order nurseries, and these are better quality trees.