Yes "New Old Stock" 10 years old I would only buy one if it was very cheap (because a lot of stuff may need changing rubber bits)
or a bike that they don't make anymore like the 2 stroke bikes NSR,KRR,TZR,TZM,Beat,Dash,Leo etc
Honda NSR150 SP and Kawasaki KRR 150 can command a good price as they have become rather "collectable"
There is also the chance that the bike looks new but is in fact "restored".
I got quite a good deal on a Yamaha Spark that had sat in the showroom for a couple of years (NOS) they changed the battery and fuel injector at the shop as it wouldn't start (no charge) only other thing that needed changing a bit fast was the tyres..other than that very pleased with it.
The rust can set in just buy touching the bike sweat from your hand can cause rust...like I said before if stored for a long time a light spray of oil on the metal bits and kept out of sun and rain will be ok.
Humidity is in the air and can't be controlled unless you keep the bike in an aircondition or hermetically sealed room.