I am confused. Are you looking at a NOS complete bike a NOS frame or a new bike that was stripped to a frame?
To me an early ‘90s NOS bike with 500EX might be worth $350+/- depending on the brand. These only sold for around $400 if that. Even a NOS bike that has sat unused for 30 years is going to need an overhaul to get new grease in the bearings.
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk