Short answer is yes, it is cheaper to brew your own beer. Not taking into consideration the cost for equipment, the cost for a 5-gallon batch of beer can be around $35-$40. Divide that up by 48 bottles and you can estimate a bottle of beer costing you just under a dollar. So that $6 six pack compared to a $10 - $12 commercial six pack, really is eye opening.
However, as many homebrewers can attest to, purchasing and consuming commercial beers can be seen as research for your next brew day. Also, I enjoy supporting my friends who have opened breweries and taste their exquisite creations.