Actually for a lot of little plants as in a SOG the soil you would need somewhere in the range of 2-3 gallon pots, but the soil expense for 50 pots of soil would be massive, making your profit alot lower. most people do a SOG with hydroponics as the medium is cheap and effective. 50 cents for a rockwool block versus 2 to 3 dollars to fill a pot with good soil.
so 25 dollars for 50 babies using rockwool or 150 dollars using soil, but if you prefer soil and want to buy that many pots and soil you could go for it.
i know that there was a man around here that just got busted a month or so ago, he had 450 plants in his basement and he had a soil-based op so it can be done.. its just expensive and tidius to water all those plants when an ebb&flow will water them all for you =D