The GM diaphragm kit for 2-diaphragm pods restricts motion of the actuator rather severely, I'd say almost in half (I didn't measure though).

Single diaphragm kit - $5 + S&H
Dual diaphragm kit - $10 + S&H
Entire NEW pod = $25-$35 + S&H
Time to replace each pod = 30-90 minutes, depending on which one


You do the math. I think it's poor economy. If you need to save that much, you might want to consider getting used pods/diaphragms from salvage yards (seriously)...