Look at the 1/72 resin figures that are on the "market". Average cost is 3 Euro per figure. It seems there is some interest in those figures. So, flats are too cheap.
The reason may be, that flats still are considered as mass figures. Old collectors painted them without lights and shadows to build dioramaswith hundreds (or thousands of figures).Nowadays painting ist an art. So, if the quality is high, it should no problem to increase the prices on a realistic (and fair) amount.