Like a house or a car, understand that you are going to have to spend a certain amount of money on an ongoing basis to tune, regulate, clean and take care of your piano. This is called routine piano maintenance. Without this care, the best piano will be sub par and potentially at risk to being damaged.
Looking for the cheapest rate from a piano tuner is pennywise and pound foolish. Your technician is your only safeguard against potential damage and wear and tear of your instrument. If you tell a tuner that you want a certain cheap rate, all you are really doing is shortchanging yourself and fooling yourself into thinking that you are getting more for less. The chances are you are getting less for less.