3. There were supposed to be more hotels around the Magic Kingdom
Original plans called for hotels with a Venetian theme, a South Asian theme, and a Persian theme. Those plans, however, were thrown out after the oil crisis. Oh, and the Shah of Iran was supposedly going to fund the Persian hotel, but, since this was supposed to happen in the late '70s, the plans were basically taken hostage and never released.
4. Admission was only $3.50 on opening day
Got $3.50 in your wallet now? Congratulations! You can now buy a bottle of water at Disney World. But not the Smart Water, there's an up charge for that.
Nowadays, a one-day ticket will run you $94 or $99, depending on which park you visit. You can go to multiple parks for an additional $60 fee, or purchase multi-day tickets for a discounted price. Which is still not cheap, FYI.