I'm happy to disclose my earnings simply because the HN community has always been very open and effusive to me in the past.
Keep in mind, I'm based in London, UK and I work for one of the worlds largest IT recruitment companies. I started this job in February (I have a few years of recruitment under my belt) and this year I will have earned approximately £60k before tax. Your first year with a new company is always relatively slow as it takes time to build new business. Next year I am targeted to bill a certain amount of money and should I surpass my target by 10% (which is what I feel I can realistically achieve) then I should end 2012 having earned somewhere around £80k. I work alongside a guy who has been in the industry much longer than me and he will comfortably earn £120k+ next year.
There are plenty of tech people who earn a lot more than me but the reality is I would never have been earning the same amount of money at this stage of my career if I had stayed working as a Developer. I've just turned 29 by the way.
In the US recruiters charge 15-30% of base and/or total comp...depends how good you are and your relationship with your client. Good US recruiters bill 300K+, great recruiters bill 500K+, and avg recruiters will bill 100-200K. How much you keep as an individual depends on the deal you have with your firm or if you are self employed.
The second part of the question ~ does being a developer make a person a better recruiter? My initial answer would be 'no'. In fact, I would argue that being a developer could hinder being a successful recruiter.
Understanding what your client is looking for is absolutely key to being successful. However, the skills that make you a good devlpr are almost polar opposite the skills that make someone a good recruiter. Being a recruiter takes a strong sales aptitude.
The other problem that comes to mind is a condition we, in the US, call 'experting'. It happens when you're candidate has 60-90% of what the client is looking for, but because you're too focused on delivering perfection, and because you know what perfection is, you neglect to send this place-able candidate in for an interview. Sometimes it's better to not know what you don't know.
Cheers
The sales aptitude gets your foot in the door, a thorough understanding of your clients business and needs keeps you there. Your argument is one of a sales orientated recruiter grasping at straws.
A significant pay packet and a 1st class client list negates your argument that a technical understanding is a hindrance.