That's more like a 6hr flight. Also (from an admittedly small smaple of 1) I was very impressed with the crew I got on AA from YYC to ORD in C.
Also need to factor in the free food/drink. Depending when it is (i.e. might still get BA miles), and you dont need the TPs, you can go HP via PHX for £280 or so...
So, assuming 1 G&T per hour at $5 each, $30
One meal and one snack, $15
That leaves a £140 premium for the bigger seat, or just over £20 per hour.
I'd be in C on HP....