Good point, Tom, and it reminded me of something I had meant to include in my previous comments: the PSI number is also related to the sensitivity of the gauge.

In prior years I used 0 - 60 PSI gauges. The pump pressure on low was near 0 and 8 PSI on high. This year I bought a 0 - 30 PSI gauge and get 5 PSI on low and 15 PSI on high. What's important to me isn't so much the number as the consistency over time of the pressure reading at the different pump speed settings, just as I look for consistency in my water chemistry numbers. A variation is easily noted and acts as an alert that something might need my attention.