Agreed. His casque doesn't look straight either and his lips aren't meeting properly at the front of his mouth. He also looks small for being just under a year old.
He looks off a bit. But why would you think he's super unhealthy and on his last leg that a vet might be the only way to save him? He may have some MDB, and some issues as mentioned above, but he could be a healthy eater and just a runt or slightly deformed. Nothing about that should make him less deserving of being with a good owner who would care and love him.
I'd be asking the seller for specifics about his husbandry and maybe even offer take it as a rescue more than a sale as it may need some veterinary care.
If you have enough experience and want to try...by all means go for it. I am all for saving it if possible, just stay open to the fact that there may be underlying problems. Good luck.