I think you're oversimplifying. Millions of people line up to buy the latest Call of Duty game at $60, but I don't think the market for those games suddenly doubles if you sell it at $30. Especially when many of those $30 buyers were presumably already going to buy it at $30 anyway in a few months.
I think it depends on how good and popular your game is. If there's only a market for 10 million Diablo 3 players, then making the game $10 won't expand your market to 60 million.
However, if you have a pretty unknown franchise/game with maybe a potential of 1 million users at $60, then lowering the price to $30 may very well double or triple your market.
If you product is junk then nobody will buy it (within experimental error). Steam sales consistently pull in a heap-load of sales and there's been lots more this year than the previous. I think if say COD9 would be $10, not $60 it would sell many more copies; go below $10 and it's at the "whatever dude" pricepoint.
Regional pricing could also be used, if the company is greedy. People living in low-income countries aren't really going to be able to afford $60 for a game, but it were $10 for them, they might.
