Why would a lot of corrupt, rich foreigners want to leave the place where they have a proven ability to profit in order to go to a place where the cost of living is higher and with which they are unfamiliar?
Also there would be some sort of screening for criminals.
Being able to travel to rich countries is a strong status symbol in poor countries, and corrupt rich foreigners risk not being welcome in their country at some point.
But in a sense you are right, such a scheme would lock out the foreigners who have most to gain from immigration.
So it's primarily an aesthetic issue? Shouldn't your argument be that paying to immigrate would not let enough productive immigrants in? You seem to be saying that the problem is it will also allow a few other undesirables to attend the cocktail party.
Also there would be some sort of screening for criminals.