This is nothing new and one can find any number of ridiculously priced vintage pieces on Ebay at any one time, but when you politely advise a seller that their prices are more than a little out of whack and they adamantly stick to their guns, you can't help but wonder if they actually want to sell.
Exhibit A. Decent condition 47 back AT-AT Commander... https://www.ebay.co.uk/itm/323092325207?ViewItem=&item=323092325207
Even a 80 graded example would only fetch half that! I suggested, with evidence of sales to back it up, that £80-£100 would be the going rate. Not in his little bubble apparently!
Exhibit B. A clearly re-sealed 21 back Luke X-Wing Pilot... https://www.ebay.co.uk/itm/Star-Wars-1979-Vintage-Luke-X-Wing-Pilot-Kenner-On-21-Back-A-New-Hope-Card-Back/323081926624?hash=item4b392ef7e0:g:QxsAAOSwol5Y0mwk
The guy is a moron at best, or a deceiving POS at worst.