How do US based web development firms survive? How do they find highly solvent clients?

I originally posted this question on Drupal.org forum (http://drupal.org/node/592560), but decided to duplicate it here, please feel free to post your thoughts here or on drupal's forum. Actually, this is a very interesting question to me.

Recently, I made a research and found out, that many famous Drupal oriented development firms (shops) are from US and Canada...and to my surprise not from China or India, where the workforce is cheap. Why is that?

Looks like there are clients, who have big budgets for web developments and they can afford hiring US based developers with an average wage of 4k/month.

For example, you're US based Drupal development firm. Just imagine, when you have, let's say 10 employees with an average salary of 4k USD, how much orders and what work load should your business have to, at least, break even. Moreover, if we go to the oDesk.com we will find out, that average price asked/offered for Drupal development services is about 15USD/hour and market is over flooded with offers from India/China guys. So if we imagine, there is some US/Canada Drupal developer who will work for 15usd per hour, this guy should work 267 hours per month to earn 4k usd. Pretty impossible to imagine, right?

So, as a result of these thoughts, there is a market exists, where good paying clients can be found, but where are they? That is the question. Those clients exist for sure and, looks like, US/Canada shops know how to find them, of course not on Odesk.com. But who are those clients and what is behind their motivation to overpay and not to stick with Indian option. Any thoughts?