Welcome to TBN.
Last year a friend of mine sold his 2006 2615HST w/loader (250 hrs) and 5' rotary mower to another friend of mine for $11,500.
A couple months ago a local person to me (about 75 miles away) sold a 2615 w/loader and backhoe on Ebay for $13,500. I tried to buy the BH but he wanted to sell it with the tractor.
I have a 2004 2615HST w/loader and heated cab with about 400 hrs. (not for sale).
I figure its worth at least $12,000 to me. Plus any attachments.
Start a little higher when you place your ad. For a ballpark figure, similar size Mahindra 2008-2010 tractors (2816's) on Tractorhouse are selling between $9,600-14,900 w/loader.