We must be lucky in Australia as standard unleaded is 91 octane, premium is 95 and ultra is 98. At the moment 91 costs A$1.24/litre, 95 is about A$1.29 and 98 is A$1.34. I was thinking of getting a chip for my 535i E39 which currently uses 95 octane. (A$1 is US$0.93) More expensive than in USA but much less than Europe!