As long as you are selling and buying at the same time you are still within the FFF rules and that's what PSG does, they release players or make sales every season to stay within the limit, there are so many players leaving this season because of the incoming ones.
For example, PSG in 2020 was losing over 200m€ for COVID like any other big club but they are the only club who spent already 70m and increased salary by 100m ish.
No this is not correct there were few team who spent so much during the covid19 transfer season, Chelsea spent about £200m without cutting players wages, mancity also spent so good amount of money too. Chelsea made about £180 from players sales so what thy actually spent was just £20m according to FFF rules and the wages of their players is still within the allowed cycle, even PSG too. The only club having salary issues right now is Barcelona and that's the major problem behind Messi new contract because they have to let go some players or cut down salaries to accommodate Messi new Wages.