Why is there such a broad range of prices for ignition coils.
 

I have a 2000 Jaguar XK8 that has been misfiring. I had coil #5 replaced 1 1/2 years ago and they had a very difficult time determining which coil was misfiring. It is misfiring again and a different shop can't seem to get it to misfire for them, so they can determine which coil it is. I was thinking of just replacing all of them. I am amazed by the number of different offerings and prices out there. I have had mechanics suggest just replacing all in the bank of the misfire, yet I want to not have them just go one by one. Are the OEM coils only sold by the dealership? Do they have the best warranty? I've read about denso coils (duralast from Autozone) Can anyone give me some advice. The car has 68,000 miles on it and I am planning on keeping it and want to make sure I have quality parts. Thank you. Janice

What King Charles is pointing out you have posted you question in the wrong section. But before you repost in the X100 section you need to have a couple of things done so that we will have enough information to be of help.
Get the codes read and have them record the STFT (Short Term Fuel Trim) and the LTFT (Long Term Fuel Trim).
The we can determine if your misfire is electrical related or vacuum related. A bad coil is going to post a P0301 thru P0308 fault code. If you are not getting that but getting P0300 (random misfire) then the other information will help with diagnosis.

I recall the coils being the exact same model whether X100 or X308; at least on the earlier cars like I have.

I have bought Denso replacements at NAPA under the store brand, and they were literally Denso in a different box, not even a label change on the part. I put that on my XJR. It was $90ish dollars for just the one coil.

I had 2 coils killed on my XKR when my coolant overflow tank split on the garbage hotplate weld seam. I bought the $100 shipped 8 pack of random chinese brand on eBay. No complaints coming up on 2 years.

100% on tracing which coil is bad. Replacing a whole bank of individual coil on plug coils seems really dumb; especially since OBD2 should definitely give you a P030X code to make it easy to diagnose. If you get a P0305, definitely switch the coil to another cylinder to see if the code moves, or perform tests on that coil; the switch and see if the code moves logic is that it doesn't require knowing testing electrical values.