Why do the Knicks need to spend 15-20 million AAV on a point guard?
Point guard has the LOWEST POSITIONAL VALUE IN THE ENTIRE LEAGUE
NBA draft, FA and trade history shows you can find a functional point guard all over. In the draft, late in the draft, in the 2nd round, as an UDFA, even in random trades. You can even find a really good one late in a draft.
Good resource management means you should spend most of your money on versatile wings. You need a rim protector who can space the floor. This is where the bulk of your money should go. Plenty of wings can also run the offense.
Part of the reason the Knicks PG situation is so horrible is they spent their cap poorly elsewhere. This is what happens when you spend poorly and use poor resource management.