Every town is different but here outside of Los Angeles we have an organization called Actor and Others it helps with a voucher/coupon of generally $20 that they pledge to help defray some of the cost of sterilization. For our puppy we got $75.00 in help and paid only 26 bucks with meds. Our cat was $16.00 after calling the local Humane Society and various organizations I Googled.
I hope that all of you who are doing the right thing and getting your loving pet a spay/neuter that you check online and call everywhere to get financial aid.
We paid $35 for the last microchip plus an 18 registration fee. The one before that was 10 bucks total. The lady who helped with the first one pasted away.
Please check around, you would be amazed at what you can find with some research. One rescue in the next town over offers good quality food to people with low incomes and seniors.