I love this sort of thing. While Google and the city govt are mired in negotiations about how to give SF free wifi, a little startup just goes around them and does it.
When your rent is 2000/month, is 20/month for DSL really such a stretch? Just asking.
If the goal is to provide internet access to people traveling in between their wifi-activated homes to their wifi-activated coffeeshops to their wifi-activated offices, well...
My rent (because I have a roommate and a studio) is $600 in SF. I also quit my job to do my startup so, personally, I am looking to penny-pinch here and there.
I also just checked my bill and I pay $45.95 for Comcast cable internet. I've had bad experiences with DSL in the past (both my own, and setting up other people's). But cable, I've found, always "just works".