I am no expert, but having some project management experience, I think about it like the iron triangle. With horses, I think it’s talent, rideability, and soundness/longevity. So things like big eq horses and U25 horses are well into the six figures. They have all the talent and scope for the huge jumps, are adjustable and forgiving and, presumably, quite sound. So then you can say, shorten a leg of the triangle. Get something that is limited in scope, price goes way down. Or something that is complicated and only goes for a perfect ride, or has a nasty spin or something else that makes it less fun to ride. That limits the buyer pool, and makes the price go way down. Or you can find something that goes great, but has a known soundness issue or is say 19 years old, that will also drop the price significantly.
I had a budget of $30k. I wanted to jump as big as possible, but I’m an adult ammy and rideablity was extremely important to. So I bought something older at 15 (less longevity although he is sound as can be), and who only wants to do the 1.15m at this point (slightly less “talented”). He also wouldn’t do for a very timid adult ammy so he’s maybe not 100% on the rideability scale that I’ve made up in my head.
If I had wanted to do the 1.30m with my budget, I could find something that was very low on rideability, for example a baby, or a complete psycho with some underlying soundness issues. Or if I needed something that was 8 or 9 (better longevity), I would have had to sacrifice scope and talent and found a 2’6” horse.