Of course there's the cost difference, but then again that goes both ways - I can find avocados, strawberries, etc. here of a quality and at a price you'd be hard pressed to find in France. Tbh, I'd argue that as far as meat/seafood/etc. is concerned, you can get better quality in SF than you can in 90% of France, where your main option will be an Intermarché or a Carrefour.

I'd also argue that the pastries you find at Tartine/Four Barrel/etc. (they typically source from a variety of bakeries from around the bay) are way beyond, in quality, what you'd find in 90% of French bakeries (the glory days of master bakers are long gone, and a lot of it is frozen crap these days, although it's been getting better in the last few years). I suspect that by this point there are more world class bakers by square kilometer in the Bay Area than there are in France, perhaps with the exception of Paris/Lyon (quite a few that I've met went to France to study baking though, so our national pride isn't completely destroyed). I bake my own bread and can buy freshly milled flour from the The Mill, which would also be hard to find in France unless you had personal connections.

But of course, I haven't gotten to the main part - which is the insane diversity of food stores and restaurants here. No matter what kind of south american, african, middle eastern, asian cuisine you want to make/eat, you'll be able to find it. That is not the case at all in France.