Newcastle actually spent a ton of money last year to stay above, they were a level of team that could have gone down, that was basically a locked thing for a while, but then they got a takeover and then they spent something like 100 million if I am not wrong, not to get "amazing" players, not superstars, but enough type of players that it would keep them at a high level.
This is why I believe that they are not really going to spend a lot of money this summer, they are doing fine. They could probably finish the season above relegation again, and they could look to overpay for more players later on to make sure that they get better, sure at a expensive rate, but slowly they will get more success and it would be normal prices to get players.
It is hard in the beginning to recruit players to a team that played near or in the relegation zone for most of the time. I believe Newcastle could be a top team if they invest on it the right way, just as City!
It requires a top manager, someone like Guardiola or Klopp and a couple of good signing. No need for top expensive players but good underrated ones that will make the surprise. Nevertheless, this needs some time, like 2-3 seasons before seeing them eventually in European spot or even in CL one.