My friend and I estimate an extra 45 seconds at every checkout for this stupid tax. I say this because they always ask (regardless if you brought your own bags) if you want new bags and it'll cost $0.10. Couple that with the fact on average people visit three stores per week, make an average of $60/hour and that there are roughly 7 million people in the bay area and you get this bag tax costing the bay area an estimate:
$15,750,000 per week in lost productivity from wasted time at check outs
(.75 minutes per checkout X 3 times per week / 60 minutes per hour) X $60 an hour average salary X 7 million people
To me the tax is insane and doesn't help the environment. It just got voted on and passed too. Just force paper bag use, and the environment would be cleaner. Simple, it'll save the economy and do more.
I realize this seems like an (and is likely a slight) over estimate of the cost. However, you can do it yourself, we waste a lot of times due to this.