It was on a whim that the Hoover Dam was added to my itinerary. I can't say I was excited about going but admittedly it seemed neat and I wanted to appease my husband, who was interested enough to fork out $30/each so the two of us could participate in the expanded tour.
The $30 was worth it and I recommend this option if it's in your travel budget. In addition to a few more "Dam jokes" than the $11 tour featured, we were able to see more of the inside of the dam and got a thorough history lesson about the building process.
The Hoover Dam is an important part of US history and literally powers a large portion of US present. This is a must-see attraction.