Kent oil pressure with standard oil pump should be around 40 psi. You'll only get this at or over 3000 rpm. At tickover, the pressure can be as low as 8 psi, and with modern thin oil, even less. (I think a standard low pressure switch is around 5 psi).
So if the gauge reads a steady 25psi, regardless of engine speed, I'd distrust the gauge.
A proper garage will have a good large gauge to screw in and check. Given you are suspecting a big bill - could be worth paying for a bit of help.
While I don't advocate low oil levels, oil starvation causes some odd readings on a pressure gauge. Before damage typically, you get good pressure at high revs then the pressure falls by a lot. I doubt you've done this.
