you are ignoring pretty much one of the fundamental laws of computing(and economics for that matter)...blahblahblahblah...HD video and near real-time editing is now becoming the baseline instead of the exception and more and more powerful computers are needed to meet the increased demand.
Not to mention that with the economy professionals now need to be more adaptable than ever. If your 2009 mac pro renders a complex edit in 8 hours while your competitor, a windows user with a brand new Dell, can do it in 6, who do you think the customer is going to choose?
I think the customer is going to probably choose the guy that gets the work done. Not the one that sits around whining about his computer not being fast enough as an excuse for lack of skill.
Have you ever worked one day in actual video post production? I'm not talking youtube videos or anti-drunk-driving spots for local cable. If you had, you'd know there's a lot more to it than rendering speed.