I've never seen an Ultimate Fallout 4 variant CGC 9.8 sold on ebay. I think that issue is a great investment book, but I don't know what one would command on ebay if listed. I am a big fan of the new series (it's the only Marvel comic I read) so I'm bias.
Its a surprisingly hard book to find. I've been scouring comic book stores all over looking for a good copy. I think most books were left unboarded, and considered just an unsold "ultimates mini-series," and therefore not kept in 9.8 worthy condition.