It's ripping people off and has obviously become so commonplace that it's now deemed acceptable. Plumbers get away with it because customers don't realise what they're doing. It's a hidden cost. I'm obviously arguing with tradesmen here so I'm never going to win am I?
I always though Cost of Parts = How much the parts cost and not how much the parts cost and an extra £500 for the plumbers back pocket. I can now see how wrong I've been and will gladly let myself be ripped off in the future.
Just want to say that had the extra costs been detailed in labour I wouldn't have a problem with it. My problem is that it was "hidden" in with the materials.
I've actually spoken to the plumber about it and told him I could get the materials @ about 75% and his response to me was to go for it and save as much as I could and that the labour would stay the same. From the comments on here on this being acceptable I half expected him to say - "But that includes my markup so I'm putting the labour charge up, then" But he didn't and I think that's because he knew he'd been rumbled. And this suggests it is dodgy.