Action Comics #1 sells for over $2,000,000.00 (http://news.yahoo.com/action-comics-1-sells-2-16-million-auction-010326975.html)
So do I. I actually think it should be in the Smithsonian ;)
I can think of things I'd rather do with $2 mil, that's for sure. But I don't find it surprising. From a Pop Culture point of view, the thing is probably priceless.
Think about it. This comic book was published in 1938, before anyone knew how popular Superman was going to be. Even though it has changed hands multiple times, even having been stolen, this copy has been handled carefully enough that it is professionally graded at very fine/near mint condition.
Judging by the comic books I've still got stashed around, it isn't easy to keep them in that kind of condition even for 15 years, let alone 73.