I don't think any star player is interested in joining the Newcastle team now. Star players will definitely want more wages, at the same time, they will definitely want to play with the same good squad and will want to win the title. Newcastle will probably provide many wages. But they can't afford to fight for the Premier League title. And I don’t think it will happen next season either. They have to slowly sort out the team.
It will take Newcastle 1 year at least to 3 years then they can attract best players to join them. Like Manchester City attracted Kun Aguero but in previous seasons, they have Robinho, Santa Cruz and a few more attacking players
Newcatsle must improve their results gradually and the investment for transfer will be very costly. We see Chelsea, Manchester City and PSG spent huge transfer fund in a decade or more to become a top clubs in the world now.
The adventure of Newcatsle will be harder because now FIFA and EUFA have more restrictions than one or two decades ago. Rich clubs now can not overspend their money like in the past.
You are right. Newcastle is now a rich club. But still they will not be able to spend as much money as they want. Moreover, even if they spend money, they will not be able to take star players in the team. Until Newcastle can come to a stable state, they will not be able to take star players into the team. It needs an experienced coach first and stabilizes the team with some medium-quality players. Then when the team is stable they will be able to include more experienced players in the team.