thanks,
well I probably would sell this one quite cheap, since it's not made in oil, or on canvas, but on paper, and it isn't an original piece of art. It would probably be below or around 50$.
If I would made a commissioned art piece like the David and Goliath, It would probably go around 100$ and above depending on the size and technique.

One of the original art - works that I'll put up on steemit soon was sold for 500 euros to one online buyer, so it really depends. :)