The cost of beer is subject to a number of factors. These days, big brands like Miller/Coors/AB are all buying up smaller labels to help squash micro-brew growth by competing as directly with them as they can. They pick companies that have solid sales and are willing to cash out....then they inch the prices up and streamline their operations.
The actual process of making consistent light beer is difficult. Lighter beers have less hops and dark malts aren't there to help mask any off-flavors. If there's too much sugar or a bad yeast mix or inconsistent temp during fermentation for lagers vs ales...the result can be a beer that's just funky. Quality control is serious business in beer making and it starts with clean equipment and being extremely careful with ingredients going into each batch. That's why most smaller breweries that aren't making HUGE volume stick to hoppier beers and try to differentiate in the ale space. Young Hipsters like that kind of beer too because it kills off the bacteria that's likely growing in their mouths from the food truck shit they eat for breakfast, lunch, and dinner. (yeah, apparently the beer isn't the only thing that's bitter...I am)
In my old middle age, I've actually switched to the cheaper beers because it gets the job done, saves money for more important things in life, and is drinkable. If you drink beer to be cool or think girls care that you only drink IPAs, you don't get it. Beer should be cold, refreshing...not necessarily light, but balanced. Too much acidity makes a nice beer to drink from a shot glass, but I don't diet that way. I want to drink by the pint or pitcher.
Now...Drinking an unfiltered lemon lager or hefeweizen at a baseball game isn't a half bad way to spend an afternoon...but only if the price is right and it's made well. I'll revert back to Miller Lite or PBR or Old Style or Hamm's or Budweiser before I order a second of a bad beer. I'm not suggesting I'd order a 12 pack of the Beast...I put my college days behind me.