Its probably based on the amount of time and effort involved...Claying properly isn't a 2 minute job!!!
How long does it take YOU to clay your car?
Plus, its once every so often, so it isn't like its something you need to do every month or so, is it?
If you don't want to pay for the claying...then you don't have to do it. It is there as a choice should you want it to be done.
Mate calm down!
Claying isn't a 2 minute job, no, but it takes a LOT less time than a proper polish, e.g. correcting swirls and light scratches. It would take around an hour on a Clio normally for me, depending on how bad it is.
£80 for a clean and polish is very reasonable, but when you want to polish a car you want the best surface to work on and you will clay the car's paint/ wheels/ glass as necessary. £100 for a clay, which takes maybe an hour or so on a small car like a Clio, compared to just a machine polish which can take anything up to... well the sky is the limit, minimum 4-5 hours though, just seems out of proportion. I would always include a clay as part of a detailing job.
Just seems a bit strange pricing it like that, but that was me just guessing all it was is a clay - perhaps this decontamination surface offers more? Perhaps Jay can explain?
As I said though £80 is a very reasonable price especially if he is doing it professionally and has overheads.