Is there any reason a signed card with quote should be going for US$730? Not any reason that I know...
Okay, gotcha. As long as you're happy. I know it wasn't me bidding against you :oohank solo: I wasn't referring to the item as potentially 'fake', but the auction itself. As mentioned by mjp, sometimes the sellers bid themselves to jack up prices.
Bukfan: The two framed ones I have are dated '63, and as per Scott Harrison they were signed to be later bound into future books by the Webbs, which then never happened. If you look at the full photo of the thing you can see that the paper is book page size, so it seems very plausible an explanation. Scott got them directly from John Martin, so the provenance is rock solid, but even he has never seen this latest one.
Just thought I'd clear this up. :)
Got a forth actually (attached), but it's not framed like the others.