An important thing to remember on the Roush and Shelby trucks is that they’re not factory packages. They come off the line as a standard XLT or Lariat and are then upfitted by an aftermarket company. In the case of Shelby, that is Tuscany in Indiana. This is important because if you go to trade or sell, there is not going to be a listing for the book value of a Roush or Shelby version. So it’s essentially worth what the base truck costs with the addition of whatever the dealer or buyer is willing to pay for the upfit package.
Personally I would just buy an F-250 Tremor Diesel if I needed a 3/4 ton; that provides a great combo of towing/hauling and off-road capability.