Mbappe and Osimhen are two top-tier forwards Real Madrid may sign right now to replace Benzema. The void must be filled before the start of the next season, or Real Madrid will be without a competent striker to fill that position, which is critical for any club. The transfer window is still open, so we can't conclude that Real Madrid won't be able to sign any of them; it might be a last-minute decision.
Real Madrid will pay more if necessary and get the best. It's in the genetics of the club. The biggest clubs in the world like Real Madrid will never be without a main striker. Benzema had great stats but now a new era begins. Just as Lewandowski scores very high goals in Barcelona, there will definitely be such a top class player in Real Madrid.
Both Mbappe and Osimhen are great options. Napoli are asking for a 200 million Euro transfer fee for Osimhen, and PSG is the only club that can afford it, the president says. If Mbappe goes to Real Madrid, Osimhen can go to PSG. Thus, both big clubs will have top class strikers.
It's said that a total fee of 840 million Euro will be paid for Mbappe in 6 years. Clubs other than Real Madrid are not subject to such a financial burden. These are truly incredible numbers. I can't imagine what the insurance would pay in the event of a big injury. But as viewers, that's not our problem. They can tie around a billion dollars to a single player if they want to. We are looking to watch the matches and have fun. That's what the football entertainment industry has become.