CC photo courtesy of ttarasiuk on Flickr.
I often see scenes similar to the above photo at Nationals Park.
Notice the lower sections of seats, closest to the field. The ones to the left and center are nearly full, followed by two sections that are nearly empty, followed by sections to the right that are nearly full.
This is puzzling at first, but it makes perfect sense once you consult the seating and pricing guide. The seats in the far right of the photo are the pink seats in the guide. They are $10 cheaper than the seats next to them in the mostly empty sections, which are at the cutoff of the higher pricing zone.
The tradeoffs of seat pricing zones are intriguing. One extreme is general admission, where everyone pays the same price. On the other extreme, Nationals Park and other sports stadiums probably have the highest number of pricing zones of any event where tickets are sold, yet there are still numerous instances where seats that are mere feet from each other cost substantially different prices.
The advantage of pricing zones is obvious: a seat right behind home plate shouldn't be the same price as a seat in the nosebleeds. So why aren't there hundreds of price zones, instead of dozens? Transactions costs would be way too high. Or, in non-economist speak: it would be too much of a hassle.