A lot of bikes can run 80+ or get over 50 mpg, but finding one that does both will require some discipline on the throttle.
I’d start by looking at v- or parallel twins in the 500-750 cc range, ideally with a 6-speed.
One little reality check, when you factor in the cost of oil changes, tires (which will wear quickly if you’re spending all your time on the highway), insurance, and gear, your annual savings will be a lot less than you think — and certainly no where near enough to cover the depreciation on that F650.
Buy the bike because riding it to work is the best part of your day and it saves you time. But IMHO, the cost savings piece is just a little white lie some of us tell our wives )