Not a scam, but reality. It appears you have an interference engine, so a broke timing belt also brings with it a high probability of bent valves and all that goes with it. None of us can predict or inspect and know for sure when/if breakage will occur, which is why the mileage and time interval comes into play.
Ask more details about the pricing variance. The higher estimate may include water pump and tensioner replacement and the least amount may only be the timing belt service. Know what you are getting. It is usually best to go ahead and replace the water pump because extra labor to do so is minimal compared to doing it later if it goes out.