so are you saying, as the four grow up they will be fine together? there is no way you can know that & is irresponsible of you as a "breeder" to do so.
it may only work if he ends up with 1 male, can you confirm this with the 4 you sold him?
you can say what you like but selling someone 4 tropheus, IMO shows no regard for the welfare of the fish or does it help someone that may not know any better.
the facts are that cichlid_fan now has 4 trophs of one type, he/she now needs to increase the numbers or run a very high risk of it turning out having 3 of the 4 dead. can you say that this is a good outcome for cichlid_fan? this is no diferent to a pet store selling someone a baby oscar or similar for a 60L tank, fine when they are small but just wait & see what happens when they start maturing.