To be fair, that job shouldn't have taken 2 hours+. Being charged 2 hours labor to replace a £5 is the sort of thing you associate with dodgy mechanics and rip off TV shows.
I agree in this case that the time to diagnose the fault was a bit long..
However...
A couple of years back a friend's bike was showing signs either of a stretched timing chain or a faulty timing chain tensioner. He brought it round to me (given he doesn't have nearly the mechanical experience I do).
The job required a lot of work. First, we had to take the fairings off to be able to get the tank off - you're looking at some 30 minutes to get it off, and 45 minutes of fiddly annoying work to get it back on.
Then the carbs have to come off. On this model that means removing the air box, which is much more easily achieved with the rear wheel removed. It's about 5 minutes to get the wheel off but at least half an hour to get it back on (several parts have to be lined up and a rear wheel isn't overly light, then there's getting the chain tension right and alignment done - some bikes are very easy to go back together some are a pain). The coils and plug cables also have to come off - but that was only a 5 minute job, and about the same to refit them.
There's a rubber heat shield just above the engine - that's something you can pretty much yank off in seconds, but again it's a good 10 minutes of fiddly damned annoying work squeezing your fingers into really tight blind spaces to get the thing properly clipped in.
Then the rocker cover comes off - basically the top cover of the engine. This is quick to take off and quick to put on, 2-3 minutes coming off, 4 or 5 going on (including some time to put some liquid gasket on).
This is a twin cam bike with a centralised timing chain (4 cylinders). Each cam shaft of course has the associated valve rockers, and although this was a fairly modern bike there's manual adjusters. They all need checking during the assembly even though they shouldn't be out of adjustment. That's often easily a 10 minute job but can me much more on some bikes (the engine has to be wound over manually to a specific position for each valve on some models, and a 16 valve engine requires 16 separate engine settings).
To get the tensioner out, the cam sprockets have to come off the shafts to give enough slack to get the cam chain off and get the shafts out of the way.
Then you can pull the cam tensioner out and diagnose what was wrong. 10 years of few oil changes and no flushes, some crud had clogged part of it's mechanism (it's a hydraulic adjuster) thus it needed cleaning rather than replacing. The part was IIRC more than $NZ400 to replace, 2nd hand ones available but the risk of them failing prematurely would not be worth the saving given the effort required.
The engine's an "interference" engine, IE the valves drop into the cylinder and if a valve is down when the cylinder is up they meet - and a LOT of damage can be done. Thus, it is very important to get the timing right. That's not a particularly hard endeavour but it does take time to do it right. Best case the engine misfires or runs poorly, worst case the engine is destroyed beyond economical repair. It's not one for the inexperienced to try without another set of eyes, and again takes easily 15 or 20 minutes - that's once you have the timing chain in place and the cam shafts mostly lined up. Again you have to wind the engine over to a certain point and then set the cam shaft into place, then repeat for the other one, and repeat a few times to make sure everything works right. You also want to slowly wind it over by hand as if you do screw it up enough it's going to stop hard, and if that's hard enough you might find a valve stem snaps some weeks or months later. That sort of failure can be messy when out on the road.
Of course there's the reassembly as well, and just for a small job on a bike, no parts replaced. More than 5 hours, 2 of us on it, one experienced one intelligent.
I've also done very minor engine work to replace a faulty crank angle sensor in a car. Some cars were made well with them being in fairly external places, others require getting deep into the innards of the engine and require the engine itself is removed than the majority of components stripped (crank case and cylinders have to be separated). A quick check on ebay for "crank angle sensor" shows the prices for varying models ranges from $6NZ to $98NZ, so the part itself could be very cheap but the labour required to remove, strip then rebuild, reset and re-mount the engine is considerable.
TL;DR Yes, some mechanics can be dodgy but many aren't. Some parts do take a few hours to replace and some of those parts are quite cheap. I have plenty of experience rebuilding bikes and a few cars.
here had been a lightning storm and since then a home PC's sound had failed. I arrived and within 2 minutes of arrival figured out that the speaker was unplugged.
While I normally check basic things, it's uncommon for lightning to unplug cables! :)