PSG does not need to spend much to compete in the French league. But this team's only target was never the league, they always targeted UCL and they spent accordingly. Now they have removed Mbappe and sold him, they need to make transfers to fill his place, for this they need to make a lot of meetings, convince the players and managers, work extra hours and at the same time increase the offers for the players they want.
I really agree with you, indeed what PSG are targeting is not French league but champions league but unfortunately their dream as not come true after gathering top players but still it doesn't work out, now Mbappe his done and he was the face of PSG and now he went to Real Madrid, PSG will find it difficult to get Mbappe replacement because he was special to them in time of scoring goal, my worry is that can PSG get a replacement fast because the season is near, I know they will definitely do well even though Mbappé is not among them, they will only fill is absent in short term before they can get partial Mbappé.
So far the ligue 1 trophy has no again the main target of PSG after they spent a lot of money in building the PSG squad so far, since PSG was taken over by the new owners, their it directly made PSG a team that dominated ligue 1 and managed to continue to win the ligue 1 trophy so far, but this did not make PSG owners satisfied and instead increased their target to win the Champions League trophy for the first time in the history club, the Champions League trophy has been the main target of PSG and that is why they continue to gather star players of their main squad so far, but unfortunately the depth of the squad owned by PSG is not supported by a good enough mentality so far in competing in the Champions League.
Losing Mbappe I think it won't have much of an effect on PSG front line next season if their can get another striker at the later, PSG have lost messi and neymar but didn't make PSG collapse as a team, so losing Mbappe probably won't make PSG collapse either, and we're just waiting for time for them to get a replacement for Mbappe.