I just got an order of SPI black epoxy and activator. The total cost for 2 gallons mixed was about $142. Which is less than the cost of 7 cans of that stuff. Not sure how much actual paint is in those cans, but can be sure that 7 cans is no where near 2 gallons.
For someone that has no compressor and only a small area to do, it may be a viable option. Other than that, I can't imagine going that route.