To be fair, people who can $9K comics are usually in a situation where they can financially meet the basic needs of life pretty comfortably, especially in America, where making $300K gets you pretty much the same life as making $2M per year (other than the size of your very nice house), of course excluding NYC and SF where studio apt's might cost you a mil.
This is true. It is hard for me to conceive of spending 9k on one comic book (especially one that doesn't have a long track record) but if someone is making 3-4 times what I do then I guess it's not a big deal.
Doesn't you concern also have to do with it being a Modern Variant?
If I was a prospective buyer then yes that would concern me. The value of moderns seems to be much more fluid. I would be concerned that I was buying at the top of the market and that it could only go down from here. It's not my money though. The buyer may be wealthy enough that he isn't overly concerned if it drops $1000, $2000 or more. If he is an avid ASM collector, a collector of these Dirty Dozen books, or whatever then that may outweigh potential declines in value.