First find out what these skis sold for new at many stores. However, watch out for inflated prices. Sometimes skis come with a nasty price tag, but then "marked down" to $xxx, which is the intended retale price anyway. Example: At Gart, we have a pair of Axis X's at $599 'marked down' from $750. No way was taht ski ever $750 that I know of! Original price- $500+ advanced ski, $450+ high intermediate to low advanced, $400+ inters, $350 and under low inter and entry.
Ask where the skis have been stored all this time. If they say, "In the garage." Ask if the garage is heated. If not, run away!
Are the bases good? Can you see any repairs? Did he was and not scrape so as to leave them in good condition for next season? if not, can you see any residual wax? Shouldn't be able too. Wax belongs in the base not on top of it. Residual wax shows the ski has not been properly waxed and therefore the bases may not be in the best of shape. Residual wax would be what I call visible, not just a trace here and there.