This is the first Home Video Game System sold in Japan. Today it´s very rare and sought after. Prices from 500-1000$ are not uncommon.

David Winter says:

"The Electrotennis is really a very rare one, very few people have it. It's worth 1200 euros alone, even the Epoch museum in Japan doesn't have it.
Nicolas Sapin sold me one through Rikard, and I paid about 600 euros for it some 6 or 7 years ago. It was a huge amount at this time, but everybody told me I made a great deal."

Here is an interesting review about the Epoch Electrotennis written by Hollo on his excellent website Super Gaijin Ultra Gamer (Japan). Please check it out :-)

The pictured variante here is the even rarer "silver" variant. Many thanks to Adam Strang who ownes this speciment, for this picture!

David Winter says: "it seems like a store exclusive. Quite possibly from Denki-ya (a Japanese electronics chain) - as there is a sticker of theirs on the box."