If an air compressor is too small for a blasting project the contractor can lose profits.
Consider how much air is required for each blast nozzle, the breathing air for the blasters, air needed for the air tools and air dryers and any other equipment.
The biggest trap is overstating the air that the compressor can supply
A compressor only giving you 120 psi may state that it will supply 150 psi from 800 cfm. Each psi less of pressor will make a 1.5% efficiency loss.
The increase in rent and diesel cost will be great but the increase in efficiency is much greater.