High blue green tree pythons is a very different proposition than something like a ball python morph. It's likely incomplete dominance and polygenic like height in humans. Most ball python morphs are dominant/recessive, which is much easier to breed for. Basically it's like breeding for a 7ft tall human vs breeding for blue eyes or brown eyes. It started out rare and is harder to get.

The long and short of it is, it's my understanding that if you can even get an ontogenetic high blue GTP, you're probably going to have to pay something in the thousands. He might want to reconsider the need for it to be blue.