As Azie says: Due to the commercial advertising rules, I can't give you an exact price. What I can do is recommend http://www.mc-market.org/forums/mc-design/ a HUGE amount of some of the best Minecraft artist's out there use that forum to get costumers.

Depending on who you ask, you'll get a different price, but the people on that forum WILL give you an amazing piece of art if you ask them to :)

Not sure. Due to our commercial advertising rules, I can't really tell you how I'd price something like this if I were to do it. It also doesn't help that I don't know how the reference you posted was specifically created. Something like that would take me a long time, so if I was the one charging it'd likely be more than someone well-versed in a better quality program like Photoshop or PaintToolSAI. Or they could be the same price. Depends on the artist's decision as well.

Thanks! However my apologies for it only be a sketch.