The manufacturers of these devices look like a bunch of unscrupulous scumbags, and their users are succumbing to what Richard Feynman memorably described as "Cargo Cult Science".
However,
recent research seems to suggest that although there is no chance that these quack devices will ever work and Royal Rife's ideas were undoubtedly flawed, he
might have had a glimpse of something real.
Plus, the item being sold seems like it could be a vaguely useful sweep signal generator. Got to be worth five bucks or so