You know beer in America was once cheaper than safe water too.
Low alcohol drinks were originaly what most people drank in addition to fresh fruit on the frontier, not water.
There is a few reasons for this.
First most people did not have refrigeration, so only things fermented would last while being consumed over the course of many days.
They didn't have ice for ice boxes in steady supply most places.
A more important additional reason is unlike in fantasy (where mountain springs are clean even in warm places), fresh water most places had bacteria and parasites such as worms, flukes, gardia etc.
Drinking fresh water was dangerous, far more dangerous than drinking fermented beverages.
Arguably drinking fresh water posed a greater health hazard than regularly consuming alcohol.
So fermented beverages were the lesser of the evils.
To a lesser extent there is still such dangers in Mexico where it is not uncommon for people to get things like hepatitis from the water.
Proper fermentation is hostile to many parasites and bacteria, as is the alcohol in the finished product.
Cider, today called hard cider was the drink of the US long before beer. It remained that way for a long time.
Children in addition to adults often drank such beverages as thier primary liquid. It was far safer than water.
Then during the large German immigration periods beer became more popular in America, eventualy replacing cider.
A big reason for that was because beer was cheap and easy to transport. It was made from a dry product that could be stored a long time and combined with water at a destination brewery. Far more reliable and economical.
Unlike cider that had to be made fresh near apple orchards, then shipped in liquid state to consumers, beer was from grain that for the amount of finished product was far lighter to ship and could be made on demand, not when crops were ready.
Alcohol today is largely as expensive as it is due to taxes, not because the product really needs to be that expensive.
The cost of a bottle of spirits for example is about 60% taxes.
Here is the data a couple years ago, and the taxes have gone up to solve various budgets since then:
Standardizing for alcohol content, the distilled spirits' federal excise tax burden per proof gallon is more than double that of beer and almost triple that of wine. The spirits' federal excise tax burden per proof gallon is $13.50. In comparison, the tax burden per proof gallon for beer and wine is $6.18 and $4.86, respectively.
Federal, state and local taxes accounted for $7.02, or 59%, of the average $11.94 price for a typical 750ml bottle of 80 proof distilled spirits in the United States in 2007.
Without taxes the cost of most bottles of liqor would be less than half the cost.