We're all on a plan at Kaiser here at Xobni. They are the web 2.0 of the hospital world, really. I'm amazed that my doctor not only has an email address, but checks and responds to it. The online lab results is pretty awesome too.

And I think they're pretty reasonably priced. I don't know exactly how much we pay per employee though.

We are on Carefirst BlueCross BlueShield here in DC, we just chose one of the smallest plans for our business. You should definitely cost it out (and it's expected). Some startups do a lump sum per month. Others get a quote from an insurance agency. If you're just looking for a financial cost, check out RedFin's financial model (they're based in Seattle)- http://blog.guykawasaki.com/2007/10/glenn-kelmans-f.html.

Can't the YC companies band together and negotiate better rates given that they already know each other pretty well?

I'll check out whether Kaiser serves Phoenix to get a hard number and I will also check the Redfin model.

This is very helpful, thank you both!