I think its completely foolish to sell away the jeep for the dress. Dear you are already married!!What makes a difference if its 1000 or 2000 euros worth dress. Instead being happy in a low budget dress just to celebrate the occasion.
I would've preferred it if they searched for a few dresses under/in budget first. If she didn't like any of these, then it's fine to consider the Jeep-selling-option. Not to keen on the boutiques handling of this, but she does look stunning and it's really nice that her husband will do such a thing for her (: