Here is equipment catalog of DEC. Mean prices is very approximate. It depends on seller: ebay, USA, England, Russia
equipment catalog
monitors / vt100 family
Model, P/N Item Mean price ~
VT100 VT100 terminal 500 $
VT101 VT101 terminal 500 $
VT102 VT102 terminal 500 $
VT125-AB VT125 terminal 500 $