What amazes me is the variation in 100LL prices. Motoring stations charge similar amounts unless they're in the middle of nowhere. Not so with 100LL which fluctuates wildly depending on where you are. Bizarre.
Probably because gross margins on avgas are a lot bigger than the gross margins on petrol, and also there are multiple ways of buying it, with significant volume discounts etc.
For example I know of cases where an aeroclub found they can buy avgas in drums for a lot less than buying it from their local AIR BP supplier.
Whereas a chain petrol station has probably already driven the hardest possible bargain with BP, Texaco, etc. I work on top of one and their margins are amazingly small - of the order of pennies per litre (which I find hard to believe but there you are). Airfields make of the order of 30p/litre gross.