It's expensive because you are talking about a surgical procedure. Would you expect a human doctor to do a hysterectomy on a woman for $70? Heck no! It would be $1000s and we have insurance to help with a big portion of it. The vet that preforms the surgery needs to be paid as well as the techs that assist and then he/she needs to pay for the overhead of the building, surgical instruments, medications, etc.
I think $70 is extremely reasonable, you are probably not going to find much better. The only other option is to keep calling around to see if you can find a better price.