They don't do a service fee, but there is a minimum. The water price is the same throughout the county, but the sewer rates vary depending on where your waste is pumped. One town is 3x the price of another, so that's where the issues with being surprised by the pricing arise. You could move down the road and your bill go up or down drastically.
I made up a sample bill below of how they break it down.
According to google the average person uses 80-100 gallons of water per day, so I used 90 gallons per person times a family of 4 for the example bill below. 360 gallons per day x 60 days (bill comes every other month) = 21,600 gallons (I will acknowledge this is WAY more water than my family of 5 uses but I do have neighbors with smaller families who have bills in this range so it must average out for people who use more or less. Especially if you use water in your yard.)
Water minimum (up to 3000 gallons) $27.80
+ usage rate of $6.95 per additional 1000 gallons ($132.05) = $159.85
Sewer minimum (up to 3000 gallons) $65.08
+ usage rate of $12.35 per additional 1000 gallons ($234.65) = $299.73
Total bill = $459.58