You're probably right Rich on the price. However I think you're only paying for the "UNIVERSAL - Mummy"-tag. I honestly can't see why anyone would like to pay $1800 for a cheaply made, unrefined piece of paper from 1951. You could buy so many much nicer posters for that money. In regards to rarity, that strikes me as odd. Why would a Realart re-release be rare? They probably printed a lot of lot, didn't they?
Could the Realart prices also reflect the idea that because any original paper for The Mummy is so scarce to non existent, that this later Realart reissue material is really the only option for collectors to have something from a time that is fairly close (20 years) to the initial release year?
It looks like it was more quickly cobbled together by Realart (from an image/artistic POV) but still, it is from one of the classic Uni horror films. 
I think both are a little correct. Beauty of course is in the eye of the beholder and yes you could buy what you consider to be much much nicer posters for $1800, but you could also buy a lot worse (i.e. daybills). As for rarity, I think we already know that it's not how many they printed, it's how many survived and even more important how is the demand compared to the number that survived.
Demand for original material from the Mummy is of course high among horror collectors and really for the $1800 this one-sheet sold for, yes you could easily get an original herald from the film (when they surface), but it most likely would not even get you a decent shape dead scene lobby card. This Realart release was the only re-issue of the film, so for 99% of the people who are interested in obtaining something from the Mummy they will have to settle for something from Realart.
But you would be surprised how rare some of the Realart material can be. When I first started collecting, a lot of horror collectors snubbed their noses at Realart material as it was worthless re-release junk, but time has proven that not only is some of the Realart material quite rare, but that it can actually be better than the original release material.
And a reminder that the Realart material is older today than the Universal originals were when I started collecting.
Using House of Dracula again as an example and look at Bruce's archives - he has only sold 4 individual lobby cards from the Realart release of House of Dracula in the past 20 years (and two of those were laminated). That's half a set in 20 years out of a couple million items sold.
One of those four cards was this fantastic scene card of the Frankenstein monster:
To me, this card is better than any original release House of Dracula scene card and probably the best Glenn Strange monster scene.
Or take this card from Frankenstein Meets the Wolf Man:
When I purchased this from Bruce's auction nearly a decade ago, people said I was crazy for paying a record price for a Realart scene card.
But to me it is a top 5 Universal scene card and is the ONLY scene card (original release or Realart) to show two monsters in the same scene and I proudly display it on my wall amongst some original cards (thanks Bruce).
I would love to complete my Realart lobby set on Captive Wild Woman, I've upgraded my original release set to all beautiful mint cards, but I can't even find the missing cards from the Realart set to complete it in any condition.
