Oil at 3$ is sold to the gas station owner at 2.50$, for example. As long as the bank threatens to take his property away from him for not paying the mortgage, he has to sell at 3$, but once enough people stop buying gas, the bank is faced with him handing over the keys and telling them that the gas tank is leaking into the aquifer and it is now their problem.

So compression of gas station rents is a consequence of the peak oil situation. It's more complicated and wholesale and retail prices can move in different directions in some anomalous times, even though they tend to move in tandem.