I dont think Piracy is the legitimate reason for the difference between AAA Companies and Indie Companies. As Anjasa said, its a service issue, not a price issue.
While there are several factors, Money is probably the truest defining point between the two. AAA Co's have access to massive reserves of cash to inject into the development cycle of a game. They can have multi million dollar ad campaigns to front load you into thinking this is to be the greatest game of all time through shear exposure before launch date. Because they front all this money into a project, they NEED to make sure it is a hit, so they try to make it as appealing to as many people as they can.
This is the end all of a AAA company. They need to recoup that money at least or they could go bankrupt after three or four such flops or loose percieved relevance after sending out flop after flop. Which again, affects their bottom line.
Sometimes Innovation can shine, but it is usually colored by AAA in that they need to be assured the calculated risk is worth it.
To draw an analogy, have you listend to the Top 40 Hits? It all sounds pretty close to the same song at the very top huh? This can be likened to the games industry when a new buzz word or feature is latched onto in the public psyche. When Metal Gear Solid Snake and Tenchu came out, there was a spike in Stealth games. Final Fantasy 7 sparked a few RPGs. FPS was out there, but Goldeneye and Halo pushed it center stage. When competitive multiplayer (done before, but perfected with the level up aspects of it) from Modern Warfare hit the scene, a BUNCH of shooters came out with a level up tread as well.
Indie companies are a bit harder to define, it's pretty much a loose term applied to everything NOT AAA. (I know, aggravating)
This ranges from two man companies like the makers of Minecraft to others a bit more heavy hitting like Behemoth or even Blizzard before WoW was launched.
It is incredibly hard to make a game (obvious, but it needs to be stated) You have to devote a ton of work into your project before you can even start seeing money come from it. There's not even a guarantee that the public will like it. But there is the silver lining that you are free to make and do what you want to. You are not constrained by a contract from a publisher that says you must have this many widgets before we'll distribute it.
And I think that was the second defining characteristic of Indie's and AAA's until a few years ago. Distribution.
AAA's like the record companies had the capital to make physical copies and provide logistical support to distribute a product. They had a desirable service, so they could dictate terms. Now that there is digital distribution from trusted vendors like Steam and Direct 2 Drive, Amazon.com, etc. There is no need to press a gold copy and make gillions of CD's and DVD's that might just flop.
Distribution has been made equal to everyone as long as they abide by the vendor's agreements. These agreements are pretty mild since the digital distributer is assuming much smaller risk than before with brick and mortar operations, so they are able to appeal to more developers.
Im sure I hit some points and completely missed others, but there's a good starting point for some of you to work on. G'night all.