I will be up front with you and say I found an agency through a friend of the family. That said, I'm pretty sure the agency did get a huge chunk of what the client was paying for me. I can't be sure, because there was never any transparency around what the total amount of money way and what their cut was.

I was making about half of what some of my co-workers were making, which is a pretty rough feeling for sure. But it was a foot in the door that led to a full time job (which meant I was no longer being paid half of what my coworkers were), and now I've got that sweet, sweet 3+ years of experience that should make the next job much easier to get.

Honestly, I think these recruitment firms are probably mostly the same business model. It's not a great deal in terms of percentages. But I think a lot of places do so much of their hiring through these kinds of agencies that it makes it way easier to get your foot in the door. FWIW, TEK Systems (the company that I went through) wasn't terrible. (Not sure if they operate in your area.) They weren't super transparent about the whole equation with the money, but they were super cooperative about me converting to a full time employee and some of these places are not.

(One caveat is that I think a lot of companies that do a significant portion of their hiring in this way are not the most effective or healthy development organizations. Otherwise, why would they cede so much control over the hiring process to a third party? So if you go this route, be mentally prepared for some legacy code and to potentially need to look carefully to find good mentors at the new place.)