I have basically the same truck you're considering and use a 2.5 inch shank with my Reese Strait Line weight WDH (1,700 pound model). The first question you have to resolve is whether you need the capacity of the 2.5 inch shank. The sticker on my 2013 F250 hitch says the 2 inch shank will support up to 600 lbs tongue weight w/o WDH and 1,250 lbs with WDH. If you don't need the extra capacity from the 2.5 inch shank, I wouldn't bother with it because, as you found, it's a lot more expensive.
My TT has a 1,500 pound tongue weight, so I had to go to the 2.5 inch shank.
If you do need the 2.5 inch shank, the Reese Strait Line does NOT come with a shank so you'll have to buy it separately. Measure you hitch height vs your TT ball height to make sure you order the right shank. I told etrailer my measurements and they sent me the wrong shank - it was either too high or too low (you can flip the shank). The correct height Reese shank wouldn't fit the F250, according to etrailer. However, I bought it locally and took a grinder to it for a few minutes to make it fit.
