She is a much nicer type and conformationally will hold up better than this guy, both in terms of soundness and ability. This guy will be difficult to truly engage and I don't like his attitude under saddle. To say nothing of his 'training'. If *I* was looking to move up a level I would take your mare over this guy any day of the week, regardless of what his current owner thinks he is worth.
To say I think he is overpriced would be the understatement of the year. $12,000.....seriously!