I'm guessing it's because the OP thinks that there is less cost in providing the game. Whether or not that's true, it's kind of irrelevant.
The price of a game, or pretty much anything in a free market is set by supply and demand. It is not set by how much it costs to produce the product. This is apparently a common misconception. It's different for regulated industries of course (like utility companies - power, water, etc), and it may not be true in a non-free market. However with video games it's pretty much supply and demand.
The lower the price the more demand but the less money get get per unit. The higher the price the less demand but they get more money per unit. At some point there is a "sweet spot" for the product. Competition is the means for lowering the "sweet spot".
So how much it costs to produce the product is somewhat irrelevant. Unless the sweet spot is below the cost to produce. For video games the cost of producing a box or delivering a download is likely very small compared to the overall cost of the game to the company. The primary costs are likely the game development and marketing, not the actual production.