Moen makes good products also and cartridges are all a swap for those (warranty).

I can change a sink cartridge, lock or a electrical fixture in a few minutes, a plumber, locksmith or electrician wouldn't walk in the door for less than $100, probably much more.

See: MyFaxI originally had a separate phone line and a fax machine that I had to replace cartridges, as well as fax machines, from time to time.

It ended up being the cartridge. 

Chart and predict on the small stuff, replace plumbing cartridges (what leaks) on a semi-regular basis and you don't get the 3am calls or the water damage.  

He charged me $120 and replaced the Moen Cartridge he got from HD for around $40, plus $80 labor!

You can buy a laser printer, extra ink cartridges and paper for less than $150 all in.  

You could copy them at staples for .10 a copy, or do it yourself with your printer own paper and ink cartridge.

First plumber came once, said my problems were due to bad cartridge in the tub faucet.

Thanks Chris - I tried to be brief in OP, but yes I'd give my original plumber another chance..... they're not cheap and his reasoning was that the part (the cartridge) needed to be ordered so he only changed the diverter at the time.....