If you do a true cost savings analysis you need to factor in your time. Apples( total cost of labor, material, freight of store bought brew) to oranges(partial material costs, don't forget the water)
Most brews take at least 6 hours (brew day, transfer, bottling/keg, and the assorted cleanup)
Even if you enjoy your hobby time should be calculated in.
Just my $.02
If you want to make it a Hobson's choice then yes factor in the time. We can never ever make 5/10 gallon batches with the cost efficiency of big craft breweries when you factor in time/overhead. However when you look at the actual out of pocket costs to the consumer then home brewing wins by a landslide each time on expensive beers. For the record my 60 dollar batch of dubbel factored in all my out of pocket costs.