The prefilter is $60 dollars from the RV filter store so it's not that expensive when you consider what it's doing. When I change out my filters every 3 months, the prefilter is dark brown with rust, dirt, pathogens and ?, so this is what is going into our tanks. There's also a multitude of chemicals in our water supply that could affect our fish over time.
For myself and my family, we have an RO
unit in our house for our drinking water, and a sediment/carbon filter in the kitchen for my cooking water.
My water is not well water, but city.