You got what you paid for, for the date that you paid it for. No one is forcing you to buy Aftermath at day one, no one is forcing you to buy MK11 at day one, no one is forcing you to buy anything, period. NRS never told you that buying premium means you'll get everything past KP1 for free or a low price. You only got yourself to blame for thinking otherwise.
Yes, it is overpriced, but you can easily buy it at a later date at a much, much lower price.
If you want things day one, you pay more for them.
What you're doing is like, me throwing a fit for someone buying a Blu-ray player for 50$ after fifteen years, while I bought the very first one for 500$.