your art is cute~
you have a nice style too c:
i would say ohh... about 4-5mil for a completed one. maybe around 500k for a sketch, notsure
i noticed on some of your drawings everything is perfect but the top head. its a little high up LOL
you should lightly sketch out the shape first, a circle, and start the hair not too far from the top
just try not to start out with the eyes or nose or hair, start out with a light sketch with correct anatomy before you start your linework
a kneeded or rubber eraser and graphite pencils will aid you in your sketching. i got a pack with all that at michels for like, $4 LOL
i hope this helps you~