I agree with the quotes from commercial places in the $600 price range for painting
all the painted parts. That amounts to about 8 hours labor at local shop rates...and is
what I paid to paint each of my bikes parts. Probably 7 hours of this is prep work and
one hour painting. Decals add time, removing old paint adds time, dents add time.
If he does a quality job, he will spend the same amount of time. So at the dollar
amounts you are offering, he is working for less then ten bucks an hour. I think I
would ask him how much time it took and figure labor based on what you think he
is worth at his skill level.....plus add in material costs. Ten bucks/hour seems a little
low to me.
Do you have a skill that he can use...maybe swap labor. He probably needs a roof
put on ... right!

Jim