As human beings, we are rather good at detecting relationships and rather poor at estimating absolutes. There are plenty of optical illusions that play on how you perceive size, brightness, and color based on surroundings. The author of Mindless Eating found that people eat more snacks if you offer them in two large bowls than in four medium bowls. Not only do people take more, but they do not notice that they have taken more, nor do they feel like they have eaten more, nor are they more satisfied.
Does “a good deal” even have an objective meaning? Probably not, but you can tell when one offer is better than another. Presentation and context still matter here. City of Heroes got good press for engaging in microtransactions: it was presented as an extra employee (not taking away from the existing staff), and the profits were linked directly to hiring more staff and getting more stuff in the next update. Players liked having the opportunity to pay more. Blizzard, on the other hand, got immediate flak for planning to sell Starcraft 2 in three pieces. The first impression was of trying to sell the same game three times or demanding $150 for the full set of units. Warhammer 40,000: Dawn of War, however, did more or less the same thing, and I did not see a backlash.
Note that this is more than cynical manipulation. You can improve the game experience this way. Indeed, that is the point of half the content: hide the fact that you are fighting the essentially the same monster by giving it a different model and slightly different stats. The people eating from smaller bowls felt no less full: they were satisfied with fewer calories. If I can make you happier just by presenting my game in a better way, I am adding value practically for free.
Most restaurants tried this with the size of their fries, drinks, and combos. One day, they were called, “large,” “mondo,” and “colossal.” Wow, a large is that cheap? And I ate the whole thing by myself, I must be full. Nothing was called a “small,” and there might have been a “medium” on the “value menu.” That was a poor manipulation that did not last, and everyone was irritated by trying to remember whether a “king” was bigger than a “biggie,” what they were called at this restaurant, and guessing what you would get if you ordered a medium or a large. I just got back from Burger King, where they changed their sizes to “small,” “medium,” and “large” (with a “value” size on the value menu). Holy crap, realism? This works on several levels. First, I suddenly like Burger King more because they made this change. It implies that they do not think I am an idiot. Second level? We are still conditioned to think of sizes the way every other restaurant lists them. When you order a Whopper combo, they ask if you want that in small, medium, or large. No one buys a small! You might not have ordered the colossal combo, but you order larges all the time. This is a great way to increase sales while manipulating people into thinking you have stopped manipulating them.