It seems to me that the recruiter might have the incentive to extract
as much as they can from the client, while also giving me as little as
Yep. They do.
In my current role - from talking to the manager I found that the
recruiter takes about 30% on top of what I'm earning, on a two month
Congratulations! You just found out your bill rate! That's the amount of money your hiring manager is paying for you. That's a HUGE advantage long term.
So, if your contractor exits the picture for whatever reason, you have the information you need to negotiate a better deal from either other contractors or just your hiring manager.
So, if your contract comes up for renewal and the contractor isn't in the picture, you can make yourself an independent contractor and get all of that, or you can call up a dozen contractors and tell them your bill rate (don't tell them the job location) and ask what they can do for you.
And yes, I'm skipping the interesting step where the contractor gets themselves thrown off site, accidently ends their relationship with you, or just lets paperwork lag, or whatever. A lot of these shops aren't well run and make epic mistakes on a pretty regular basis.