Yes, despite the cost, it can be a very tempting offer because it is about the only way to get access to a boatload of Destination Points now at anything approaching a "reasonable" cost (whatever "reasonable" means in the world of points).
Look at it this way, for someone with a Maui Ocean Club Lahaina/Napili villa 2BR OF Float week worth 7475 points, buying 3000 DPs at a cost of $34K or so instantly elevates you to Presidential level. If you paid $25K for that week resale, your total cost would be around $60K all-in with closing costs, etc. That's about $5.73 per point. At Marriott DP prices, that same 10,475 points would probably cost over $115K. Someone with two of those weeks, could buy 4000 points at a cost of about $45K. Added to the $50K cost of those two Maui weeks, the $95K total cost for 18,950 DPs is about $5/point, versus over $200K from MVC.
That's obviously an extreme example, but it's not hard to find other examples with only slightly worse numbers. In today's post 6/2010 world, there aren't many other ways to get boatloads of points that cheaply.