New iMacs with built-in VESA mount adapters revealed, cost $40 extra
 

Bemoaning the fact that those new slimline iMacs weren't compatible with your VESA mounts? Well, the problem has now been (kind of) solved, with Apple's online store adding the option to buy its desktop models with built-in VESA mount adapters. You'll have to pay for that reclaimed deskspace, however, with $40 added to the prices of both the 21.5-inch and 27-inch families. You'll also need to purchase the stand separately, although your old VESA arms will be compatible. Alas, if you've already paid up for your new iMac, there's still no word on any transformation kits just yet.
http://www.engadget.com/2013/03/14/a...dapters-costs/