I wouldn't say it's extraordinarily valuable, especially as an opened pack, but it's a very nice find to be sure. They're likely very well-made - while modern custom decks have some great finishes, sometimes the registration and stock quality can leave something to be desired. If the estimate of late '70s-early '80s is correct (and I'm inclined to think it is), these were made by Arrco before they were bought out by USPC in '87 - the Tahoes were generally well-made cards and popular among players and magicians. What condition are the cards in?