how much would it cost

to paint all the plastics on an x 18 pink?

well you would need 2-3 cans of paint.Krylon works the best for plastics at 4$ a can. depends if you want to put a clear coat on too and remember to sand the fairings with 400-600grit sand.paper

wont spray paint chip off though?

not if you sand all the fairings first and do a good job with everything