Is the Ford dealer taking advantage of me?

Yeah I get that, if they put a load of hours into a car to find it’s not a warranty item then the owner has a nasty surprise bill.
There is however the reverse scenario. My mums case was a genuine warranty repair, but they scared her off so she actually went to an independent garage to get the clutch repaired as their quote was significantly less than the AD. It was only because the independent effectively refused the work as he claimed there was no way wear and tear had caused the clutch to fail on such a new car and it should be addressed under warranty. If he hadn’t been so honest and confident about it she’d have ended up shelling out to replace a defective clutch. How many others have gone down this route for what should have been legitimate warranty claims?

Can't say it's the case for this shop, or for all brands, but the mechanics I deal with have told me repeatedly that the "book time" allotted for many warranty repairs is not enough to cover the time it actually takes (brands don't just screw over customers, but mechanics too). So yes, I believe there is an incentive in some cases to have them take the car elsewhere.

I have an outstanding recall on my ‘06 Audi for the airbag and I still am getting notices for it. Very surprised that a safety feature that is mandated is not universally covered.

The first thing they did was look for DTC codes which may point to a no info from sensor message. Then they pull the sensor plug and look for power,ground,communication. If one is bad then the test wires for continuity from sensor to module. This part may take time and a lot of digging just to get to the modules and connections, so they want cash.
It may not be the power, but I was being brief because internet.
They want cash upfront because the get a lot of refusals to pay because nobody believes how complex a modern car wiring is especially one with safety nannies.

Finding electrical, wiring faults in a modern car can be an exercise in frustration, it sounds like the dealer isn't quite sure where the fault lies and wants to cover themselves for the search. It's only going to get worse as we jam more electronic features on our vehicles. I learned from an enthusiasts site that my Focus ST has a BMS (battery maintenance system) that needs to be reset when you change the battery to get the best performance out of the new battery. Sure enough, there is a 16 page Ford Service Bulletin about the system and why it needs to be reset. I had never heard of it, it wasn't in the owner's manual.

I can’t comment on whether your particular case is unusual, only comment that electrical problems can be a bear to troubleshoot. I’ll give an example of a problem I had in my Ford (a 2007 Mustang). This happened circa 2015.

I was having intermittent problems where the car would suddenly go into “limp home mode” at highway speeds. For anyone who has never had this happen, the car basically restricts the max RPMs, speed, and throttle response because the computers have detected something wrong and don’t want to damage the engine. Codes suggested Mass air flow sensor and throttle body, so I replaced those parts myself. Still happened.

Took it to my independent mechanic, they spent several hours trying to troubleshoot (at about $100 per hour), traced it to a control module, and told me to take it to the dealership because they didn’t have the tool to program a new one if it needed to be swapped.

So off to the dealership. They also concluded it was the module, swapped it out and programmed it, but the car kept doing going into LHM. So they started throwing even more parts at it - none worked. They had the car for weeks, and I was getting frustrated.

Now the difference in my experience compared to yours is the shop was very upfront with me that they were not going to charge me until they figured out what was wrong, and also were not going to charge for the parts/labor to install said parts until they verified it fixed the problem. They eventually had to call in a Ford engineer from Detroit to troubleshoot this. Turns out it was a bad solder in one of the fuse boxes that had probably been there from day one and had eventually broken.

Upshot of all this was they charged me for a new fuse box and the labor to install it, and a little bit of diagnostic time. But that’s it. I asked about all the other parts they had swapped in, and the service manager told me that Ford had told them to write them off - it wasn’t worth their time to remove them and put the old parts back in and also not fair to me to charge me for work that didn’t solve my problem. I ended up with several thousand dollars of new parts on an 8-year-old car for free.

I do think in you case, charging a fee in advance is a bit over the top, but I do think you should expect several hours of diagnostic work to isolate the problem. And simply switching out the sensor might not be the correct solution - I suspect they have already tested the sensor and found it works, so the problem is likely upstream from it.