Just to make sure there's no confusion, goldensc -
Although the title you chose for this thread is "RL Purple Label Suits," and in your initial post to this thread you refer to suits, you do realize, I trust, that the eBay auction in question is not for a suit. It is for a jacket/sport coat.
I did, just now, search eBay for "ralph lauren purple label (sport coat,sports coat,jacket)," in Completed/Sold listings, in the category Mens Clothing:Blazers & Sport Coats, and limited results to "New w/Tags." Even ignoring past listing by the same seller as the one in the auction to which you refer, prices tended to be in the hundreds of dollars - not thousands. So the price being asked by the seller in the auction you mention seems about average - certainly not "unbelievably low."
As I have little experience with RL Purple Label jackets, I have no idea whether they usually sell for $3695 in the real world. Maybe they do. I simply couldn't say. For all I know, they may have an MSRP of $3695, but sell all the time, at nice brick and mortar stores, for far less than that. I wouldn't know.
I do have experience with Brooks Brothers jackets (and suits, pants, shirts, etc.). I routinely see them selling on eBay, often in condition ranging from "Like New" to "New, with Tags," for a fraction of what sell for in a Brooks Brothers store. I would have no difficulty believing that something similar holds true for Ralph Lauren.