What's the deal with high dollar Webers
 

The market is not rational.

If it were, people would be buying Honda Civics that can trounce early 911s.

You're referring to the 46IDA Webers at the high prices, and they were used on the 906, 911R and a handful of other very limited production cars. so: rarity and genuine-ness make them costly.

Just a bit of background, not justification for prices, by any means. Some years back (10-20 or more) the Weber group in Italy closed down production of all the 3 Venturi carbs, and moved the rather worn out tooling to a factory in Spain, later, I guess it was moved again to Eastern Europe somewhere.
Collectors and those who prize originality, value the made in Italy Webers over the layer ones. You can see the Made In Italy on the float bowl sides..
Just be glad you don't have Ferrari Boxer, which needs 4 off these!!

I just saw a set of early 911 seats with an asking price of $5900 so its not just carbs.

Quality was much poorer on the non Italian webers. We purchased several sets back in the day, and the Throttle bodies were so bad it was impossible to tune them. One thing to be very careful of, is that the throttle shaft and shaft bores wear out very quickly on these carbs, so buying a used set is risky, especially at today's prices. Throttle body re building is expensive, and to do this properly requires specialized tools and a flow bench to test after the work is done. According to Pierce Manifolds, who rebuilds our throttle bodies, it was not in common for the throttle bodies to be significantly worn by thirty to fourth thousand driving miles. This causes excess air to be drawn in there, which can cause a lean mixture on some barrels and spitting back through the velocity stacks

i sold a set of 46's in 30 minutes for $4300 3 years ago. Probably worth more now but I don't think I will find another set. Sport Seats are in the same catergory.