Your comment, however, IMHO, is quite correct. The best horses (for our purposes) THAT WE CAN AFFORD. I think for the vast majority of amateur riders, we HAVE the best horse we can afford. I don't know of anyone who says, "I think I want to do dressage, I have $5K, so I'll go out and buy the LEAST suitable horse to do dressage." But the horse one ends up with may not necessarily be a WB. Appropriateness and suitability are also factors. We make compromises - young horse/old horse, trained/untrained - what is the best I can do for what I am able to pay? Being advised to go into debt to get the supposed better horse - not such a good idea, UNLESS you are so totally focussed on FEI levels and/or winning and/or the team that it becomes a necessity for you. And even then...a risky proposition if you cannot AFFORD to take a loss due to injury or eventual mental or physical unsuitability - like that winning Young Horse competitor referenced by Betsy Steiner that essentially "quit" when he hit second level - those marvelous gaits being a little too difficult for him to contain and he didn't WANT to do it.
Being told that you won't improve your riding without such a horse is also... I'm trying to find a word.... not quite irrelevant, but something like that if your goals are smaller and perhaps more focussed, as we say (sigh) on the journey rather than on winning per se or reaching FEI levels in the immediate future.
I am going through the ups and downs of dealing with a supergreen big moving 3.5 year old, purchased at 2.5, unstarted. I am riding at the limits of my ability and holding on by my fingernails. Another horse probably would have been more appropriate or more suitable, BUT... I could not AFFORD a more trained and equally good moving horse. While I may be a little too old to be dealing with a baby horse, I'm also too old to be dealing with an older horse with possible soundness issues - which is probably the only way I could have afforded a decent WB with training. But to imply that one cannot improve as a rider and cannot do good dressage unless one acquires a five-figure WB....I just can't get behind that