They tend to say that, it makes the most money. As with all mechs these days, they pick the highest price part and base the fee on that rather than simply fixing the lower cost ones.
If you can get hold of a super cheap analog type voltmeter you can easily hook it up to the abs sensor leads and spin the wheel to read the pulses, if none the sensor is bad.
A/c clutch if bearing not dead could easily be cheap man's rebuild to go for years longer and maybe 50 cents doing it. And why on earth would you then view it as necessary to buy the whole compressor over that??? I have never bought one ever and just keep working on the outlying parts to get the a/c back up and running for years more. Buying a compressor as the 'cure' is what most of the unlearned do and you should know that most people who do it then still never get the a/c running for long after that, they simply do it all wrong assuming the new parts 'fix everything'................they DON'T and OFTEN. I based my incentives on that when I was in parts. I'd bet based on my own experience that easily 60% of all a/c system spent money does nothing there. I certainly saw it happen enough. People think new parts cure everything but not in a/c, the lack of knowledge is the 800 lb. gorilla there, can't get around it.
On the alternator testing..........someone should be able to show the result of the 'ripple' test, or the diodes, if one is dropping out to come back in can easily be your idle flicker issue, it can come and go. The later Focus alts are positively horrible about it. New alts are a disaster now and apparently rebuilt by people who never went to school. 50% are bad right out of the box.
Window regulator? Commonly rebuildable by the owner, often at very low cost. I've rebuilt mine before at zero cost.
Foglight coming on/off can be simply corrosion on contacts, you clean them up and coat with bulb grease and no more trouble, did both mine a little while back (year) and not a peep of trouble from them since. One was not coming on at all to then start working an hour or more later, or not at all. Perfect now.
Driver's seat probably fixable with no cash outlay at all. You have to LOOK AT IT then THINK, or how you make money out of thin air.
Uh, only an idiot would leave a check engine light on for years and absolutely that person does not belong working on cars.