I don't think the website is working right yet.
Here's the one I use:
Ford Build & Price - 2010 Ford F-250 SD
I can build a 2010 6.4L F-250 XLT longbed 4x2 with automagic tranny, but with no packages, interior options or exterior options. So the MSRP is $44,415 (or 47,655 with 4x4). But after you add the pkgs and options, the price will probably jump up there in the 50k realm.
I can build "your truck" except F-250 Lariat 4x4 longbed limited slip diesel and automagic tranny and get to $50,320 with just those drivetrain options. But still no packages, or interior options or exterior options or accessories.