That's expensive in my opinion. Also, they probably have them because they're not based in the UK (despite the domain name) and that the PSS seems to be more readily available on the continent. This was more or less confirmed to me by Michelin CS (also on the continent) who told me that the 225/40 R18 92Y is freely available. When pushed and asked several times why a) it wasn't on the Michelin UK website and b) why it was difficult to get a hold of in the UK I was merely repeatedly furnished with sales guff about what a great tyre it was and that I should try them out. I would if I could, pal!
Overall, it was a futile exercise contacting them and trying to get a satisfactory answer...