that fade effect will cost no less than a grand and a half if it done by a hustler. a good painter will charge you with in 2gs
its not the amount of colors that will cost your for this job, its the fact that you have a fade with a variation of tone. thats a load of labor right there.

i have 3 colors on my bike. it cost me 800. your tank design is too fancy and tanks are the hardest part to paint.
^ forgot to say that from the get go......

 

That seems pretty high for a motorcycle paint job. Motorcycles are very easy to paint because every panel being painted can be removed. I'd shop around some more, you'll find someone that can do it cheaper.