I've been running the Bay to Breakers for over 20 years, and I've watched it go up in price every year.
I was thrilled to find that for 1 day, Halloween, they are discounting registration to $31.10. It goes to $49 the next day, and I believe it will be about $60 closer to the race.
If you've never done it, you've got to. It's more than a bucket list item, it's a tradition!