He is the top scorer at Manchester United this season and this clearly indicates his performance is still above average. On the other hand, the impact given is actually quite large because indeed how many fans he brings if he changes clubs and the sales from Marchendise and Jersey are still quite worth it for now.
No doubt Ronaldo performed very well last season despite Manchester United's poor outing, he was their best player of the season and also the club top scorer so moving to new club he will also perform well and the club's finance will be increased too as as result of his signing.
Regardless, from the start it seemed that Bayern were not too interested in Ronaldo.