You are right - i worked for a big big vendor company(offshore/onsite model) for around 5+ yrs. My rates has been varied from $200/hr to $68/hr depending upon what role is being offered by the client organization(NOT vendor organization). But this vendor company had a lot of overheads-Non Working managers(Assistant Engagement Managers, Engagement Managers, Group Project Managers, Delivery Managers and above) and a huge bench strength(ranging from 10%-30%). So they used to have a very good cut(margin) over my billing rates and i was getting fixed salary. There margins at some of the times were in the range of almost 65%-70% also but one thing was good with my big consulting company that when i was on bench-i don't have to worry about the job(recession free career). So my job has pros and cons both. In fact during the bench time - i can do some self learning to help myself in future projects/career.
I am seeing since 2004/2005 - Independent contractors and vendors having no offshore component are facing tough time to get very good billing rates. On the contrary it's hard to get very good billing rates in USA(for private sector contracts) if you are not having EAD/Green Card or Citizenship. Though for public sector projects - local american based companies can get very good billing rates.
For independent contractors or employees(H1, L1 etc...) from very small companies - the billing rates i am talking about are almost 25%-30% lower than what i mentioned.
In a nutshell - i never negotiated my billing rates ever - it's how much my company made the client pay for myself. For the higher billing rates projects - hourly rates of $150 or more - it was too much pressure to deliver(plus weekly travel) while anything in the range of $80-$120 - it was reasonable project. As and when my billing rates were lower than $80/hr - i can make out my employer is falsely trying to convince me that it's an architect role(it was Tech Leader or Sr. Developer role). During entire 5+ yrs - 15% time client was paying $150 or more, 45% time client paying $80-$120, 35% time $80 or lower while 5% time i was on bench. Moreover all the $150+ billing rate projects were very short in nature - around 2 to 7 months. I believe this can give you a very good indication of the billing rates for the last 5 yrs.