Why - PC Install Technician AP Professionals Employee Review

I was hired at AP Professionals as I was an intern for the company I was going to be contracted out for. The company I was being contracted to already knew I was a good employee but wanted to hire me on contractually. I don't understand why this company would pay AP say $50 and AP gave me $25 per se. I don't know for sure how much they were getting paid, I just know it was significantly more than I for next to no work. I don't understand why contract companies are allowed to exist.