Is she pulling my leg with some kind of sales gimmic to try to get me to buy the $400-500 a night rooms ? ?
No, she is not pulling your leg. It's the basic laws of supply and demand. They know that time of year if you won't pay the $ someone else will. I do extensive travel planning, both business and personal. I agree with staying outside but as close to the park as possible. It will be less expensive. It will not be the same experience as staying in the park but should be just as enjoyable.
Another tactic to get inside the park is to book something outside with a liberal cancellation policy and then keep checking to see if something opens up in the park.