It is a DISA made tripod for the MG3 as you noted and depending once again on where you're trying to buy or sell the price varies considerably. They're still available here in the states for about $400. I have no idea how much where you are...Sweden isn't it? I saw some for sale in England at the War and Peace show in 2011 for 700 sterling so a bit more in UK than here.
Looks like its missing the box for the optical sight/persicope and the battery box which was a separate piece. The sight box was attached to the rear of the mount in front of the T&E. It contained the sight, filters for the sight and I think a couple tools for the lafette. Looks like the rest is there.
Hope that helps some......