What I meant was the process of purchasing gas is a relatively free market (within a regulatory framework, of course). By free I mean that I am free to use or not use gas, I'm free to choose whatever station I want, and I have complete transparency in what price I will be expected to pay.

I was not refering to the larger issue of the transportation network and all the various subsidies and incentives in place...

Oh, I understand.  And I'm not trying to argue with you.  I'm just trying to  remind everyone what "not buying gasoline" means in this day and age.  It means opting out of "the system."  And (as all peak oilers know) the system is based on gasoline.
Yes, agreed that few in the country can opt-out of gas consumption directly (except those of us in urban/mass transit areas). Even we have to have most of our food delivered by trucks, so indirectly we all feel the pain. Also, we still have school buses, police/fire emergency vehicles that all need fuel. So I guess unless we go off the grid, we are all in the same system (more or less).
Transport won't make a big difference in the cost of food.

Take lettuce or baked beans as an example.  A semi-load of either might be 60,000 pounds; driven from San Diego CA to Chicago IL (2145 miles) in a semi getting 7 MPG, the load would require 306 gallons of fuel.  Increasing the price of fuel from $2/gallon to $5/gallon costs an additional $918, or an extra 1.53¢/lb.

These fuel costs plummet if the freight can move by rail.  If the railroads aren't looking at ways to run express freights with power for refrigerated containers, they're going to leave a lot of money on the table.

The thing is, between increased transportation costs and petroleum fertilizer, not to mention farm vehicles, the cost of food WILL go up. It's not just transport.