Judging from the prices on
www.rvtrader.com, that seems to be a fair price.
Even more importantly than a rear ladder, make certain that everything is working or fixed BEFORE you sign the papers. With the market today, you don't want to be shuffled off to the warranty department for repairs. It could be in there for months waiting for repairs.
People give Camping World a bad rating, but it depends on the CW you're using. Ours used to be horrible, but I've had good service lately.