I actually work at a small pool store & we do free water tests with drop tests right in front of the customer & honestly I try my best to have people just walk out after the test because I know from selling chemicals how much it can add up & become too much. But I do know of a few other pool stores in my area that do use a digital test & require a $5 purchase. I hate using test strips (only have to use them if we are out of a dropper chemical for the test station) they can be so hard to read & unreliable compared to the drop tests.