This one was sold by someone for more than $2,600!
The unit and the box aren't even in excellent condition.
I checked mine (with original box and instructions) and it appears to be worth between $60 and $80 (seen ending prices from $31 to $110 depending on condition of box and country of sale etc.).
I'll keep it for nostalgia sake.
EDIT: It appears the presence of a box and its condition make a big difference in the price; I knew they were important, but it seem to make the toys worth a heck of a lot more (I thought about that some more while noticing 6 Million Dollar Man dolls up for auction.
I believe ones with a box in excellent condition can fetch 5 times the price or more.
My two brothers and I (young at the time, so we didn't think of putting the games in a suitcase) had some Game & Watch toys stolen by a hotel employee while we are at the pool or eating a meal.
Those (I forgot which games) might have been worth more now than DK.
I think Flagman was one of them!