The oil pressure gauge on my 931B is leaking so I priced one out from Finning(Cat) and they want $88 for the gauge and $4 something for the rubber gasket that goes around it. This seems like ridiculous prices to me. The part number was changed and the new gauge looks kind of cheap compared to the original. I can get an aftermarket gauge for under $20. Thoughts?
My thoughts are you answered your own question. Price is ridiculous and you got hosed most likely. If it's a mechanical gauge, buy a good quality truck aftermarket and move on.
You could also try one of the many outlets like Offroad Equipment who sell both genuine Cat & aftermarket over the same counter. If you go to them with a Part Number they will usually offer you as many sourcing options as they have in stock to allow you to make your own mind up which suits your budget.