There is a caveat/exception to that above rule.
The whole point of a Platinum sale is to bulk-buy the 2000 Platinum option for cheaper. Regardless of a cap or not, players will definitely take advantage of that 2000 Plat for long term usage. However, a Platinum sale during a cap with players already buying Platinum will encourage them to buy more 2000 Platinum deals, thereby allowing profit to be further increased.

It's not the Platinum sale that will augment profits in this case, but rather the introduction of a new elite cap that possibly snatches back some players from other games that will augment the success of a Platinum sale instead.

I know it's confusing, but think about it and it should make some sense.

AvidLegend has a good point as well though. Nevertheless, is it not agreed that a Platinum sale would mutually benefit everyone, players and developers included?