system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is malt liquor significantly less expensive than beer?
gpt
The first malt liquor was an attempt to deal with a shortage of materials in WW2. Barley, that you would normally use for malt, was rationed. Experiments started taking place to replace the use of malt with materials such as sorghum, corn syrup, etc.

So, how alcoholic a beer is depends on the amount of sugar that yeast can't convert into ethanol. More sugar= More booze.

After the war, some breweries decided to take their experiments to market. The most famous, of course, is Colt 45. At first it was marketed as an upscale alternative to beer. It never captured the buying public, until they discovered a whole different market.

People, mostly inner city, who wanted more "bang for the buck" in an affordable form.

Now, up until the craft beer revolution (made possible with Jimmy Carter legalizing homebrewing), the quality between malt liqour and beer was pretty equal, really. If Colt 45 really worse than Budweiser? 

With the resurgence in craft brewing, however, malt liquor was left to languish in the cheap section of cheap liquor stores...it's quality never having gone up.

So long story short, malt liquor uses cheaper ingredients, hence the price difference.