There are plenty of houses in Tracy, CA, about 50 mins east of SF. You can get a 4 br 3 ba house for around $250k. It was also one of the "ground zeroes" for the housing bust, because those $250k homes were going for $650k in 2005.
You can drive 20 mins west to the Dublin BART and be in SF within 30 mins. My commute was 50 mins every day without traffic, so it ends up being comparable.
I think your numbers are a bit off. I live in Livermore (25 minutes West of Tracy), and it takes me at least 45 mins to drive to SF (if there's no traffic). It's nice that BART comes as far as it does, but it's a 45 minute ride to SF, and that doesn't even include the 15 mins (30-40 from Tracy) drive to get to the station.
I get your point that Tracy has available housing, but I think a 1.5+ hour commute makes it a much less appealing solution than the 50 mins you mentioned.
You can drive 20 mins west to the Dublin BART and be in SF within 30 mins. My commute was 50 mins every day without traffic, so it ends up being comparable.