Prices that you mention looks pretty close to Canada. I pay fuel 1.20 a liter right now but normally it is more like 1.40 a liter, that is around 16 pesos a liter. Milk is like around 6.40 for 4 liters, this translate to around 18 pesos a liter or 70 for a US gallon.
I really do not mind if the price in Mexico is like in the USA, if it is worth going in Mexico, I will pay what it cost. I have seen many very beautiful places on photos from Mexico by the beaches. USA is getting very crowded in the south and to find a place near a beach in season is nowhere near a reasonable price. All the beach area in Florida are condos and hotels and the more you get to the warmer Florida in winter, the more the prices goes up and piled up in the campings.
Arizona deserts BLM are very cheap, but this is the desert, when you want more, you pay more.