Warmbloods in NA command a price premium because they are fairly scarce and tend to be purpose bred. Even the mediocre ones are more expensive than other breeds
The OTTB are very affordable because they get rehomed when they retire from the track.
QH are by far the largest breed numerically and they have lots of different types. The QH/TB cross can be a very versatile lower level sport horse.
So can the draft/TB cross which was the recipe for the “heavy hunter” type in Britain before WB were introduced. And is still an affordable cross these days in Canada
A WB is going to cost significantly more than any OTTB or TB/QH or WB/draft cross of equal ability. In North America the WB is like a designer label, elevating the percieved value of the animal.
It’s about scarcity and marketing.
Some experienced horse people in North America have done well importing WB from Europe because even with the shipping and quarantine costs, and the bother and risk of shopping overseas, the total cost is significantly lower and the job of finding a horse much easier (if you have the right connections and agents).
So that right there tells you about the cost differential.
My feeling is that a WB for a middling income junior would be a “step up horse” not a first horse. You’d start out with a stock breed (we have some adorable appaloosa ponies in our barn currently) and then maybe get a well broke TB that had long forgotten about the OT part of life :). Most juniors never jump above 2 foot 9, even when competing.
The jump up to 3 foot and above requires a full retooling, usually a new program, and always a new horse. I know one junior that did this going into being a young adult, and her parents had significant income. She competed a bit locally, not sure how much or how long. But yes, that required a mid 5 figure WB almost ten years ago now? And another trainer barn world life.