Blast from the past.
Returning to Melbourne from Western Australia in an Army convoy in late 70's, we pulled into the servo at Balladonia to refuel the trucks. Drums of fuel had been delivered to the servo for this purpose, but we had to pump it by hand.
There were around 130 military personnel involved, and we headed for the 'munchies' section.
Then we found out the cost! ... Pie and sauce, $4.40! ($1.15 in Melbourne)
I asked one of the locals at the pumps what a pie normally cost, and he replied "About $1.60?"
Allowing for the fact that Balladonia is isolated, that seemed reasonable, so the word was rapidly passed around that we were being ripped off by the servo, and all sales immediately ceased. We opened ration packs, and ate them while sitting outside.
The Operators had known that we would be there to refuel for awhile, roughly knew how many soldiers were involved, and had stocked up accordingly thinking that they had 'captive' customers.