Howdy, after listing to the dripping finally went to get a replacement . Man $50 was a shock but then when i got home- it was missing one rubber sleeve so i returned and the plumbing supply guy gave me the package of 2 with springs ( that likely costs $1.50). So i replaced the cartridge and rubber sleeves and rubber rings that come with it. no more leak which is great.

But now i wonder was it the cartridgee or the rubber install sleeve?

So plumbers when you have a dripping leak how do you rule out the really pricey cartridge/ do they leak and cause a drip if they fail? Or is it the rubber sleeve and o rings? I wonder as $50 is worth avoiding if not necessary...