You're right! It's the sewer rates that will kill you!
We used to pay our water/sewer bill quarterly. I remember the highest bill I ever paid was $108 and that was in the summer when we took more showers and I watered the garden. they generally averaged about $50 a quarter.
Then the city decided to combine the water and sewer bill with the monthly electric bill. The city claimed they didn't make any change but I ntoiced that my MONTHLY water/sewer bill was averaging $50.