I must admit, the psychology of pricing games is interesting. I wish one of us had thought about doing a topic like this in the earlier days of this wonderful site.
Anyway, Check-Out is a good one for discussing psychology. The prices of typical grocery items (not all of them) change, probably sometimes almost weekly or daily. But just think of how hard the game can be if a car (or some amount of cash, probably during Big Money Week) is at stake!!! I have to give honorable mention to Pauline here. I remember my reaction to her Check-Out win, and I can tell you that I was downright amazed, and I was also shocked!!! When I saw she won the way she did, I literally felt like my jaw had almost dropped to the floor like Genie's did in Disney's Aladdin!! I never thought I'd see the day when someone would win Check-Out perfectly!!!!
Check out is an interesting case since there are pretty much two ways of playing the game.
1) Trying to guess the exact price of each individual item
2) Trying to guess the total price of all 5 items combined
In Pauline's case, she tried to play using strategy #1, and while she did ending up getting the TOTAL price exactly right, she was quite a bit off for the last 3 items (on youtube search: Check out Exacta) :
Item #1: 1.39 | ARP: 1.49 | DIFF: 0.10
Item #2: 2.69 | ARP: 2.39 | DIFF: -0.30
Item #3: 3.79 | ARP: 2.99 | DIFF: -0.80
Item #4: 3.99 | ARP: 3.49 | DIFF: -0.50
Item #5: 6.49 | ARP: 7.99 | DIFF: 1.50
Now contrast this with a contestant named Thomas who highballed the first 4 items, and bid a dollar for the final item (YT: Check out just squeeked by) :
Item #1: 3.00 | ARP: 0.99 | DIFF: -2.01
Item #2: 2.50 | ARP: 1.99 | DIFF: -0.51
Item #3: 4.00 | ARP: 2.99 | DIFF: -1.01
Item #4: 6.00 | ARP: 3.99 | DIFF: -2.01
Item #5: 1.00 | ARP: 4.56 | DIFF: 3.56
Thomas' case is interesting because he instinctively knew he had highballed, but never actually knew by how much since the grand total isn't displayed until a guess for all the items is shown, so his actual last bid was really a shot in the dark.
This makes it so that each individual guess isn't worth much as the total amount is. It may even be more taxing to try to exactly price each item, than it is to just think of a grand total number. Pauline missed the final item by $1.50 which in many situations could make or break a playing. It just happened to work in her favor.
Which is why I'm kind of waiting for a moment where a contestant bids: $0, $0, $0, $0, $20.