There are two gift shops located at the hotel. One has your normal trinkets and do-dad's and the other is a little more expensive. There is also a nice book stand in the Visitor's Center. I like to collect penny's that have been run through those stamping machines.
What to buy: Not too far from the Visitor's Center is the Service Center (Camp Store) with gas, groceries, etc.
Our favorite gift shop was Big Mike's, right on the main road heading towards the park. Marie calls these kind of stores "crap traps" because they sell everything and it's impossible to come out empty handed!!! This place was cool; we both ended up leaving with different types of pottery, shot glasses, dog tags, marbles, stones and rock carvings. Highly recommended!!!
What to buy: Depends on what you like, but the most popular gifts are rocks and rock carvings/pottery items/art.
What to pay: Most places are comparable; we each spent between $35 and $40 at Big Mike's.