To me, I'm only interested in snakes that have good to great feeding response and if they're really young I don't care as much about what they're fed (as long as it's size appropriate). At that age I feel like there's two problems with taking the breeders word for it. First everyone's definition of "great eater" is a little different. There's no agreed upon terms of great eater meaning takes every meal. A snake could refuse once a month and some would still consider it a great feeder. And who knows if something fasts at the year mark or not, it's all a gamble really, so the breeder's statement of being a great feeder doesn't really mean a ton to me.
So for me I just look at hatch dates and weights to see how well something as fed so far and go off that. For a banana YB male I'd say you're looking at about:
Amazing price - 150 or less
Decent price - 200-400 depending on quality
Rip off price - 600+ (I rarely see this price unless it's unique, like it's also a paradox or het/poss het.)
Other than that it all depends what you're looking for. I'll be buying one more banana in a year or so and it has to be a male maker, so even if I find a male banana with multiple genes for a great price I'll have to make sure it's male maker, if they got the boy from a banana x banana pairing then the price would have to be REALLY low for me to be interested.