That kind of defeats the purpose of bringing in people who have specific skills. Furthermore, as a former H1b myself, I know that the salary has to satisfy the Department of Labor's prevailing wage. If you want to make the salary threshold higher, no need to turn it in to an auction, just set the bar higher.
I decided the US wasn't for me after three years and moved overseas. I then worked 1099-MISC for another American company for four years (until it was bought by a company with an international office near me). If I can do that, what's the point of capping H1b numbers?