Always give year, make, engine size and model # when asking questions.
There are no Kawasaki dealers in your area - closest is Crazy Freddy Massapequa - their prices won't be any better.
You're getting charged so much because a valve adjustment takes close to 2 hours (which they probably don't perform because the valve adjustment interval on that engine is about 4 times in the life of the bike).
Perhaps you don't need a full service.
Specify only an oil & filter change and top up all fluids.
If you simply don't want to do business with them, call Champion Honda (Hicksville Old Country Road) ask if they will do the work I just mentioned.