$90 for 4 oz of Issey seems high to me to. I have a big bottle of it I got a long time ago that was not nearly that expensive,. and maybe I am wrong, but I would expect Issey to be past its hey day and available at a discount various places. Someone would would probably be willing to sell you a big decant. 4 oz sounds like a life-time supply. Issey is strong and tenacious!
Check Target for Issey. I recently saw it there (about 2 weeks ago) on clearance and I think it was about 30 bucks for the 1.7. I think Walgreens (online) sells the 2.5 oz for under $50. No reason to pay out the nose for this one.