Is there something wrong with doing that? He specifically disclosed the year of his reference. If a potential buyer wants a more up-to-date estimate, they can look for one.

I don't think the comparison to TCR is good. Many more people collect/sell Nevada. There is a lot of data supporting the values. Quoting an old TCR would appear to be lazy or sneaky. If you don't collect PR, but have only a few chips to sell, do you NEED to have the latest guide to sell them? If I collected PR, I'd have the latest guide before I purchased.

Again, he disclosed the reference, plainly. Caveat emptor.