Black Mask Press have become masters at the making of collectibles for comic book conventions, especially those written by Matthew Rosenberg.
Young Terrorists #2 has a confirmed sale elsewhere of $30.
The Forevers #1 has a confirmed sale elsewhere of $125.
But Four Kids Walking Into A Bank #1 SDCC Exclusive?
Limited to 50. Kept a mystery until the show. And it is still a mystery
Well, it looks like this.
It's just that no one I can find online seems to have opened them. possibly because, unopened, they have sold for up to $355 on eBay.