It's one of those "imagine a frictionless, perfectly spherical pig in a vacuum" theories that don't survive contact with reality.
Buyers don't just pop up on timestamp zero and remain unchanged. They anticipate price changes, potential new buyers come in, the market is dynamic.
I also don't understand why this only affects monopolies. The same logic should dictate that all products and services fall towards MC?
Yes, the logic applies to all sorts of bargaining situations - that's what later papers mentioned in the article is about
I am not an economist, but I think that the theory is that prices do go to MC in a competitive market. Coase's theorem was for an uncompetitive market. (In fact, a monopoly - the most uncompetitive market possible.)
> The theorists, most notably Gul, Sonnenschein and Wilson and Fudenberg, Levine and Tirole, formalized Coase’s insight and showed that under quite general conditions the logic goes through. Which is rather surprising, since, as Tim and I point out, Coase’s conjecture implies that many patents and copyrights are essentially worthless — a prediction wildly at variance with the facts.
The authors themselves had the same reaction.
It's similar to physics: you make small simple models, you investigate what they say, you compare to what you get in reality, and then you make adjustments.
The interesting bit is: what kinds of friction or airpressure or shape do you need to add to your pig to recover what parts of reality?