The doctor used a low-cost disposable flow meter to measure the flow rate of the fluid he was measuring. The disposable flow meter had to be low-cost, otherwise disposing of it would not be very wise. Any disposable flow meter would have to be low-cost, or people would not want to dispose of them. Not disposing of a contaminated disposable flow meter could mean cross-contamination between people or food. Of course the doctor I went to knew how to properly dispose of a disposable flow meter.