You can drive across the hoover dam or walk across the hoover Dam and see the Hoover Dam for free without any tickets.
But when you want to actually get a tour of the Hoover Dam or park at the Hoover Dam then you'll need a ticket for the Hoover Dam parking and Hoover Dam Tours.
Parking is $10.00 at the Hoover Dam.
The cost to have a tour of the Hoover Dam Visitor Center is $10.00 per person ages 4 and up.
And for the Hoover Dam Power Plant Tour the cost is $30.00 per person.
The cost is well worth it and it's a wonderful thing to see and a great thing to do with your kids as well.
I would highly recommend visiting and touring the Hoover Dam and the Hoover Dam power plant.