Bingo...when you account for time there is almost no way you are coming off cheaper than buying it. Lets assume $20/hour x 6 hours for a typical AG batch...that is $15/6 pack, just in labor. Way cheaper to buy, and that's not counting equipment or ingredient costs.
Much like everything else ever said in a LHBS, saving money on beer by homebrewing is BS.
This topic (whether to count the cost of time in valuing the net benefits of brewing) has been done to death, however as an economist who does cost-benefit analysis for a living, I feel like this is the one place on these forums where I can weigh in with specialized knowledge. Feel free to skip this post if you're not interested.
Point #1: In theory, one certainly should count the "opportunity cost" of your time, which may be $10 or $20 or $50 an hour or more, depending on what the value of your next best option is--if you could be making $20 an hour at work instead of brewing at home, then that's a good estimate of the cost. Of course, most of us probably don't have the type of job where we can just work extra hours and get paid extra for them on a whim--we're either salaried or work hourly but with a fixed or semi-fixed schedule, and can't vary our schedule immediately if, say, we wanted to work an extra six hours on a Friday evening instead of brewing a beer. For that reason, the amount of value you place on an hour of "free" time is probably somewhat less than what you'd be getting paid in (post-tax) wage, although economists disagree on exactly how much the discount should be.
Point #2: if you're going to include non-monetary costs in brewing (like the opportunity cost of your time), you had better include non-monetary benefits as well, like the benefits you get from the act of brewing itself. A lot of brewers (like me) get real satisfaction out of going through the brewing process, and that has a value which is just as real as the value of time forgone in brewing, albeit hard to measure. This should be included in measuring the benefits of brewing even though you don't get any direct monetary benefit from it.
To me, the opportunity cost of my time is pretty well canceled out by the enjoyment I get out of the act of brewing--just like when I sit down to read a book, the enjoyment that I get out of it is at least worth as much as the cost of time I spend doing it, otherwise I wouldn't do it in the first place. If you assume that the non-monetized cost (opportunity cost of time) is about equal to the non-monetized benefit (enjoyment of brewing), you can basically disregard both when calculating net benefits.
Which brings us back to comparing actual monetary costs--the marginal cost of inputs (grains, hops, water, yeast, fuel) and the fixed costs (equipment)--with actual monetary benefits--the savings foregone by not purchasing more expensive beer. And according to that calculus, beer is certainly cost-saving, which is the point I was making earlier.
Of course, if you get little or no enjoyment out of brewing beer, then yes you would of course want to account for the opportunity cost of time in evaluating homebrewing's net value to you. For me (and, I suspect, for a lot of others) the benefits of brewing, as opposed to the economic value of the beer itself, are big enough to outweigh that. So yes, brewing is cost-saving.