Here's an interesting approach to selling Smartphone games... ChronoTech has created a generic engine for games that supports a number of essential features and they have created several games based on this engine. This approach is something that most game developers do - what makes ChronoTech different is that they are selling the engine rather than individual games. After you buy the engine, you get a free copy of every game they create based on it. Right now, they have four games:

"Cave Adventures - More powerful than boulderdash and supaplex.
Soko World - Sokoban style gameplay.
Yellow Man - You are a yellow man that must collect dots and avoid ghosts.
Sea Mines - Minesweeper variation."
The trial version lets you play 1 level of each game. The full version is $9.99 and has thousands of levels. Check it out! So that's less than $10 for 4 games - plus the promise of free updates containing more games in the future. Sounds like a good deal to me!