I suspect a lot of people will plunge for the PMI Old Lady now that it has "safely" reached 81. Which means the the people who "risked" buying at the lower discount points ... bore the risk for no significant advantage. From now until 6th December, it essentially an ordinary sale.
If Michael had said "we will limit the number on sale to 90" ... then I think the 81 figure would have been reached even faster. Some people's thinking would have changed from "well, I'll buy if it reaches 81" to ... "I can't risk missing out on this. I'll jump in sooner, rather than later".
Another option would be to have the discount start to reduce AFTER the upper limit had been reached ... but just for those people who agreed to jump on AFTER 81.
40 to 60 = 50%
60 to 80 = 60%
80 to 90 = 55% (for the late arrivals)
90 to 100 = 50% (for the very late arrivals) ... or whatever
The upside would be that I think more people would jump to buy sooner, rather than later .... and the optimal price would have a greater chance of success. The early buyers would be rewarded with the best price ... but the late arrivals might still be attracted to a very decent bargain... but just not rewarded as much becuase they didn't take as much "risk".
OOooooh. Think of the mind games.
But then again, maybe this is a solution in search of a problem.