I don't want to take this off-topic, but AG brewing is much much cheaper than Mr. Beer.
I can make 10 gallons of beer (five TIMES as much beer) for $20. Actually, 10.5 gallons of my cream ale cost me $17.97 in May when I made it. Making two gallons for $20 isn't cost effective.
I will agree, however, that it's a great way for new brewers to tip their toes into homebrewing. Kinda like the bunny slope at the ski hill- you gotta start somewhere. My friend has done Mr. Beer for at least 10 years, and she has no desire to make anything else as she's happy with her Mr. Beer set up, for the most part. She dumps out a lot of beer, but she drinks quite a bit of it too. It works for her, and probably many others.
But no way is it anywhere near a commercial craft beer in quality, and that's the thing. If it cost $20 or so for 2 gallons of Mr. Beer, but $20 for two great quality six packs, I'd go with the one gallon of great commercial beer everytime.