Well, if you were hoping to setup a lush planted tank with schools of tetras, shrimp, and corydoras then I can I understand why it wouldn’t matter what these fish are.
Have no clue what prices are in Canada and agree the tank is overcrowded but he gave you some nice fish.
The price on dats varies wildly based on quality and type but it and the aro could easily fetch a $1000 or more, particularly as they get larger. There are all sorts of peacocks but that particular Kelberi is a lot nicer than most I’ve seen nowadays.
Also, it would’ve been a good idea to keep the datnoid and get rid of the two common plecos.