It's just hype. There are no tournament staples in the set, and the only card that is (almost) impossible to get a hold of is Thunder dragon (played in reanimator). No one needs to buy this set, but a lot of people want to buy it. At least, for $35: everywhere where you could preorder it for the suggested price the set is sold out. At that price the set has good value if the cards would be normal versions. As a collector's set, it has some additional value. That's where supply and demand come in I guess. ATM supply is very limited. Somehow I doubt demand will be high at $100...
Wizards can use this hype very well. They can make as many collector's set as they want. Reprints of the dragon sets, but also Angels, Zombies, Elves, Lands... As long as they limit supply, they're assured that the set will get sold out.