Perfect Binding With NO LABOR!

Right now I use a Minolta C6000 + Perfect Binder. It does a good job but I was hoping to see if there are any other better solutions. The current drawbacks are cover stock is limited to 350 gsm. Each page costs $0.01 black and white. Our pages are 6x9" generally. We max out around 425 pages using 20 lb paper.

I don't want to hire someone to manually perfect bind 100+ books per day. Would love to hear some thoughts.