These regulations will become a game changer. Arguably, should have these rules been in place now, Mbappe coudn't have signed his new contrat with PSG.
The new regulations will see clubs subject to squad cost controls for the first time. The cost control rule restricts spending on player and coach wages, transfers, and agent fees to 70% of club revenues. (The gradual implementation will see the percentage at 90% in 2023/2024, 80% in 2024/2025, and 70% in 2025/2026). This requirement provides a direct measure between squad costs and income to encourage more performance-related costs and to limit the market inflation of wages and transfer costs of players.
https://www.uefa.com/returntoplay/news/0274-14da0ce4535d-fa5b130ae9b6-1000--explainer-uefa-s-new-financial-sustainability-regulations/