Though for this to work it still relies on you advancing through the game at a rate comparable with your purchasing of KP.... and to take it to the extreme level - once you complete all of the storyline that is so far available then you won't be increasing your coin output after that.
The players who are posting that they have 2m KP costs
are at the end, and they are fine. They can easily grab 10m+ by visiting on the map, and probably have 10m+ per day in excess coins as well.
The last couple chapters increased coin from residences by 10-20%, or 15-30% if you have 150% culture as many players do.
To increase your cost from 2m by 20% means buying 800 KP
At 2 chapters per year, that's about 4 KP per day perfectly sustainable, especially since the cost increase isn't done as a %, it's a flat 500 coins but your income goes up much more so it will take more and more KP purchasing to catch up to economic growth.
The thing is, even if all of the KP buyers are wrong, and they reach a point where KP starts to get too expensive, they can always switch to the wholesaler
then. Handicapping yourself
now for a problem that may or may not happen in the future makes no sense especially if you can change tactics at any time.