I agree that SF is a dirty city, but there are nicer parts of the bay area. I think the parent was talking about more than numbers, though focused in a different area: what Silicon Valley creates.
Consider how much time you spend using things created in the bay area: Google, Facebook, Apple, YouTube, Yahoo, Twitter, LinkedIn, Ebay, WordPress, Pintrest, Reddit, Instagram, Paypal... the list is too long to name everything.
I'm living in the south of Sweden near Copenhagen and will be going to a open-source dev meet-up in Copenhagen today in fact. There's not the same Valley feeling perhaps but there is a startup and dev scene.
The region is really really productive technically. There are lots of startups and some do really well. Skype (Swedes, Danes and Estonians), Spotify, Mojang (Minecraft), Dice (owned by EA; Battlefield etc), Massive, etc etc. Lots are in the game-making space.
There are lots of big companies too such as Ikea, Ericsson, Saab, etc etc. Names you recognize.
And Sweden is a really really big exporter of music; the third biggest exporter in the world, or something like that, which is not bad for a population about that of London.
Of course many want to move to the Valley and I know many who have. But having been over to visit a few times I'd much rather work remotely from my farm house deep in the Swedish countryside with my great broadband.
Consider how much time you spend using things created in the bay area: Google, Facebook, Apple, YouTube, Yahoo, Twitter, LinkedIn, Ebay, WordPress, Pintrest, Reddit, Instagram, Paypal... the list is too long to name everything.