$80 is for the annual pass. I buy this if I plan on seeing several national parks during the year, because that covers entrance for all of them, and for everybody in the vehicle. I see people planning trips to the West including Yosemite, Sequoia / Kings Canyon, Death Valley, Zion, Bryce, and the Grand Canyon. The annual pass is a no-brainer in that case.
If I am just seeing one National Park in a particular year, I don't buy the pass. Why would I? I just pay the entrance fee. I'm pretty sure most other people can figure that math out.
For the majority of people, vacations are planned and budgeted for. Entrance fees, camping fees, food, fuel, and souvenirs are all part of that budget.