I guess it would all depend on how well the figure was painted and also how much someone is willing to pay for that figure.
I have seen plastic foot figures sell from $4.50-$10.00 each and the quality has varied very much from figure to figure with better painted figures sometimes selling for less then figures that looked like the painter was blind folded???
The price of the unpainted figures would facter in as some figures are more costly then others. And some figures have much more detail and colors per figure or require more time and tecnique to complete.
Mounted figures,flag bearers and drummers ect. would be more work also and if a figure is to be converted as well as painted that could add to the cost also, even more so if the conversion requires parts from various figures.
Myself I couldn,t be bothered with trying to paint for profit. I like to paint figures when I,m in the mood and don,t have to many to paint at once, taking all the fun out of it for me. I,m no great painter but I think I paint a figure to a point where its good enough to mix them into a diorama with a bunch of other figures and have them look alright when seen in mass but to even to get the figures to that level it takes me quite a bit of time and the time it takes me to paint a figure to that standard I can,t see selling the figure for $5-$8 like most painted plastics sell for??? Besides when I create something like a conversion or my self painted figures it has a personal feel to it and I don,t want to part with it.
I guess if you really enjoy painting them and don,t mind parting with them and can make bucks its a different ball game.
So to answer your question from what I have seen the average price for painted plastics is average between $5-$8 each but Quality of the paint job and price of the base unpainted figure factor in as do mounted figures and flag bearers.
I have seen mounted figures from $8-$15 each and flag bearers around the same as mounted, depending on the flag detail.