I think it all comes down to the client screening. If the service works as advertised and saves you significant time finding good clients, increases your rate b

I think it all comes down to the client screening. If the service works as advertised and saves you significant time finding good clients, increases your rate because you have more worthwhile options to choose from and so can charge more, and/or gets you projects that are more interesting and fulfilling to work on, 10% is cheap. Tons of developers give up a much higher cut than that to work at agencies for those exact reasons.