IO320-360 = 8gph at cruise
Well its all relative: 8 USG/Hr = 30 litres/hr = £62 per hour of Avgas as opposed to say a Taylor mono ~ 3 gallons (Imperial) per hour mogas = 13.6 litres = £20 odd (depending on the inflated price at the pumps)
For 100 hours per year that is a £4k difference. Coming back to the original post, that is about 1/3 of a Rotax!!