Mmmm, smells a bit fishy tbh.
Still:
Never buy a watch to sell it afterward, it's a false good idea. There is a reason ADs NEVER get you more than 5-15% of MSRP on Rolexes, it's because you just always find a buyer for a new Rolex with that rebate.
If an AD proposes a 50-60% rebate on a specific Rolex, it's for a good reason: it's simply not selling (for a long time) and Rolex ask each AD to have a minimum turnover on their brand and have their pieces sold before they can place a new order. So the AD is organizing some 'private sales' to get rid of those pieces and be able to place a new order of the 'easy to sell' models (for instance: Rolex, Subs/DJ/daytona, for Omega, Speedmasters, for AP, ROs).
What it means, is that you'll be hard pressed finding someone to re-sell this piece to, or a second hand dealer who will be interested in swaping the piece for something else, you'll be most probably stuck with a watch you don't like and nobody really want to buy from you (except at a VERY marked down price, which means you'll lose money).
That said, if you like the Ball, and the price is better than the best price for a new one on Chrono24 (a quick search tells me around $2k), go for it, it's most probably a good deal