How much are 23k gold plated pokemon cards worth?

My husband was rummaging boxes in his parents attic the other day and found his pokemon card collection. Among them were all six 23k gold plated pokemon cards from 1999: Togepi, Jigglypuff, Charizard, Poliwhirl, Mewtwo, and Pikachu. They all still have their casings, Poke-, and certificates of authenticity. We are looking to sell, but would like a feeling for their worth (if any). All items are in great condition, like new. How much would they be individually, would they be worth more if sold in a set, and where should we look to sell them? Ebay doesn't look so promising. Please help!