Most went for a batman comic (this was recently after most of them had seen The Dark Knight...) and were surprised to hear it was Action Comics.
Guesses as to why?
"first one in colour?"
"first one with a lesbian kiss?" (I just love this kid.)
"last one hand-drawn?"
"Did it have a wombat in it with rainbow coloured poo?" (Err... No. Therapy required?)
Most kids hit on the idea that it was the first of something - M___ finally settled on first Superman comic.
We used a form on Google Docs for this one, and got kids to input a lowest bet and highest bet in a form.
No-one was anywhere near the $1,000,000 it went for. Seriously, not even close, and till i showed them the story a lot were unconvinced.
"How much did it cost when it came out?" ($0.10)
"When did it come out"? (Wikipedia tells us 1938)
"Yeah, but how much would that be now?" (Great question, we took a few guesses - all were too high, mine included. Went on DollarTimes which told us it'd be about $1.50)
So if i'd bought it in like 1938 ... "
(This devolved into a spirited debate about the possibilities of this: "you weren't born then..." "you'd need to have a time machine" "if he had a time machine he could just go get it now.." "my time machine broke down next week" - this made me chuckle for a while. I have stolen this gag, and passed it off as my own since!)
"Yeah, but what if i'd bought it now...How much money would i have made?" (We worked out he'd get 666,666 x his investment. We had a bit of a conversation trying to work out how much first gen IPods etc would be worth given the same inflation.)
Three days later i had kids in my room at lunch time looking for comics just about to start a run so they could buy first editions and make a billion pounds.