That is pretty decently priced honestly... I would charge more. I was in the collision repair/refinishing business for a few years than got sick of it.
FTR, if you are painting an entire car and it has plastic bumpers, you WILL mix two different things of paint and add flex agent to the bumper paint. You have to have the bumpers off to do a good paint job anyways so... Personally, when I painted a couple of my own personal cars, I just added flex agent to all the paint. Took the bumpers, hood, trunk and doors off, sprayed all the edges, jams etc... and put it back together than blasted the whole car...