I think it would be unfair to bidders to post figures but your numbers are at least not far of the range.
The feedback I can give is that it is soooo hard in grade. Not sure how or why, but the little time I spend in here I sense that people seem to forget that highest grade really change the game on key books.
I spent countless hours to get hold of the single highest AF15 9.6 back in the day(is it 3 or 4 now?). The price range from various posts on the boards was close to half of what I considered correct. End of story I wake up to "breaking news" that CC sold it for 1.1kk(I was not even offered the book!). A bit higher than my price, but MUCH higher than what I was reading in here. Now I might be happy that I did not get it; but I still sense that the original old label 9.6 is the best.
Countless times on other important DC silver I hear that "ohh...I had a raw that was just as nice....bla bla...". But with this BB28 you don't really get any of that. So that is why I replied to Foolkiller even if he probably know already.
"Any price" is to stretch it, but it's not really for sale at anything close to current "market value". With the stock market at all-time-high weekly there might come someone along with a mad offer; but if I am earning on rising shares it might even out?
The irony of it all is that I love later sliver more than this book(most of it low value). Also I think that the JLA #1 cover is way cooler the BB28