I remember seeing one attendant using binoculars to check out the prices of the station down the road from them.
I also remember a radio station's competition where the petrol station that sold fuel at the lowest price won the competition. In the final hours of the competition, there were two or three stations selling petrol at 1c/litre... and they lost to the station that was paying customers 1c/litre...
It was about 10 years ago, I can't really remember. Something like $10-20k? Maybe 50? It wasn't outrageous, but it was enough to get a lot of petrol stations competing for it.