Without knowing the rest of the deal being offered, I can't comment on whether the dealer's really offering you something good. He may be.
However, if you must know the absolute most Rubi wheels could cost, take a look at Mopar's website. They sell them brand new. (Mountain ones too.) But with Mopar, "overpriced" is an understatement, so you might also take a look at Quadratec's website to price out new wheels with a similar look.
The bottomline though is that with Wranglers, there's always folks taking off their stock wheels and getting new ones to go with lifts and whatnot. Try running a search on eBay or Craigslist, I don't expect you'd have any problem getting some with just a few miles on them should you pass on the dealer's offer.