I would agree with dogpaw on this one. That particular work of art could easily be worth 1mil. It's pretty dang good quality. You should price art on how much time, effort, and most importantly, on the quality that you give. Also, if you give the person who commissioned you a beautiful drawing but it wasn't what they had in mind, that might end up decreasing the price-- unless, of course, it was better than the person had in mind.
So, technically, if you wanted to, this could be worth more than 1mil.