Beauty does say that some boys seem to treat their horses kindly, in particular one boy who sells vegetables with an old pony. "The pony followed his master like a dog […] and rattle down the street as merrily as if he had come out of the Queen's stables" (41.9), Beauty says. Jerry calls the boy "Prince Charlie," saying he "[…] would make a king of drivers someday" (41.9).
Beauty also describes an old man with a coal cart who has a very close relationship with his old horse, and Jerry says, "[…] it was a comfort to think how happy an old horse might be in a poor place" (41.10). So basically, money isn't necessarily the key to a horse's happiness.