Ask artists what they can accomplish in a given amount of time. Different artists work at different speeds with different subjects. More experienced artists may be more expensive but more expensive artists tend to work faster and have a better idea of what they are doing.
I made this in fourteen hours around August 2012:
Sure, it's detailed and all but when I made this, but it looks amatuerly done when you know what to look for. The leaves do not make sense, and this tree isn't particularly interesting. That, I also could not draw everything else in the same style as trying to draw other things are out of my skill level. Say I worked for $10 which is dirt cheap - that's $140, and that doesn't cover the fact I redid this tree in a completely different style. Luckily, that was merely for a volunteer project.
I made this in three hours at around October 2013:
Over a year later, I know a lot more about art direction, and I drew a tree that is a lot more expressive than my other tree. Colors are more exciting which can communicate a fantasy setting more strongly than my other tree. Let's say I theoretically worked for $40/hr for this art style. I blew up my theoretical rate four times higher (which isn't even a rate I'd actually ask for) and you get a tree that's not as expensive as the older, less skillfull artist I used to be.
(Sorry if these images disappear in the future... I uploaded these on dropbox)
