You pay for what you get really. Airbrush work is expensive if you find a GOOD artist/bodyshop to do it, and it looks awesome, can last the life of the motorcycle, and it will never wash off or weather. Decals are cheap stickers that look like stickers they can look alright but they will never be custom to you. Be careful with do it yourself airbrush stencils, you can cause a bunch of problems if you are not familiar with the refinish process. Think about it this way if you spend tons of money in aftermarket parts like exhaust, wheels, fat tire, forward controls, etc. Why go cheap on the graphics/paint? Remember paint is the first thing they see and the last thing they remember.
This is just my opinion, coming from an airbrush guru.