the substitute issue was also part of the reason for the "draft riots" in NY (and other cities too) since new immigrants were sometimes 'drafted' to serve right on the dock as they got off the boat, but middle class and others could by there way out, with $500.

Yep, right off the boat...they had the recruitment stand right there at the ramp. "Lookin' for work, mate? $300 a month and a fresh uniform, you can't find better work than that. Just sign right here." Little did they know their "position" was cannon fodder. BTW, a scene in Gangs of New York illustrates this recuiting "maneuver."

And the substitute fee was $300 dollars at the beginning of the war. Think they raised it as manpower became more crucial because of losses and desertion.