Had a friend buy a new Camaro body from one of those companies and he spent a pretty good amount for it. Having said that, the body he got was as close to perfect as I'd ever seen and he didn't have to do ANY body work (aside from prepping for paint). All of the original parts he had bolted right up & fit well and, when all was said & done, he was very pleased.
$18K for a Bronco body would be tough to stomach but if that was for a complete body "kit" (tub, fenders, hood, ws frame, tailgate ), then it might be worth considering if building a show vehicle or something "new".....