I paid under $2.80 for 85 in my 4Runner and the Focus' premium fuel fillup was right at $3.01/gal.
I'd like to see a dyno chart showing a diff between the octanes and see if we're actually making noticeable gains since octane doesn't make horspower it's just the higher octane is more resistant to detonation. I notice a bit better throttle tip-in and a little better MPGs on my Focus but I doubt I'd see a diff in say the 1/4 mile consistently and maybe a tenth at best.
in my STI I obviously have to run 91 but if I go put 101 octane race gas there'd be zero diff unless I raise the boost (sport sharp mode adds a few more psi) which is the only reason I'd run higher octane but really just for track duty.
'12 Focus Red Candy SE Sport 5 spd
'99 Toyota 4Runner Sport
'11 Subaru WRX STI Hatch