The cost to fill your swimming pool with city water depends on your cost per unit of water from the city.
For me I pay $2.00 per 1,000 gallons of water which is a unit on my water bill so for me it takes only $10.00 to fill my 5,000 gallon swimming pool which is pretty cheap.
If you pay a truck to come deliver the water it can cost a few hundred dollars to even $1,000.00 so it's best to fill the swimming pool with your city tap water because it's much cheaper even though it will take around 9 to 10 hours to fill the swimming pool that is 5,000 gallons.