Prices dropped pretty hard on X-Men LEs a few months ago because of major software issues. Long story short, the software was buggy, many disliked it, and an update didn't come soon enough for some people. This, along with the normal cycle of early NIB purchasers selling once something new and shiny (Avengers) came out, led to alot of them being on the market at the same time. Prices dropped pretty hard, but I can't say that I saw more than 1 or 2 ever get as low as the $5250 you mention.
Since then, a good software update came out which fixed most of the early concerns, and more goodies are rumored to be in the pipeline. This, combined with the fact that many of those that were on the market found their way into new longer term homes, is causing the prices to head back up towards "normal".
If you can still find one for $5250, I would say that's a really good deal at this point. I would expect them to settle around $6k in the near future, if not a bit more (especially if there is one more update that really kicks butt). I can't imagine they would go down any further, so I would be shocked if you lost much if any money down the road. It is a fantastic game...many who have given it an honest chance since the update consider it to be among the best Stern machines made.