Normally, used saxes are about 40% of new. I think you can ask the seller to lower the price a bit, even considering the included set-up.
Probably would not need to be set up again unless you're rough on your horns or it falls out of the case, etc. Even, so this is not usually a big deal and should be inexpensive. Ask about the pad condition, as replacing all the pads is expensive.
If this is from a reputable business or repairperson, i think you would be fine to buy before trying. Yanagisawa are very well built and very consistant, so it's rare to find a bad one (I never have). Ask the seller if you can have a 7-day trial period. In that case, the worst that would happen is you would have to pay for return shipping. Good luck!