In the end it'll probably be about the same, it really depends on how much it costs to deburr/ remove the sharp edge left after a punch.
I ordered 3 42% SS sandwich cases for a custom my friend and I were making and they cost $50 each, if I expand that to 24 cases it ends up being $39 each (done through big blue saw). The only way I could see a 40% sandwich case costing $80 is if you only order 1, are getting some special finish (anod, powdercoat), or are using a different material (cf, brass, copper).
Does your cost factor in the custom die needed for the stabilizer holes?