“Let me tell you how it will be / There’s one for you, nineteen for me / Should five percent appear too small / Be thankful I don’t take it all.” These lyrics from “Taxman” by the Beatles are the clearest explanation for the main reason spirit-based seltzers are more expensive than malt based ones: taxes. In this country, spirits are taxed higher than any other alcoholic beverage, much to the chagrin of spirits companies. The root of these high taxes goes back to Prohibition, and comes out of the characterization by teetotalers that spirits, above all else, are the most evil alcohol.
There are other factors that contribute to the high price as well, including the price of ingredients being used — it costs more to brew and then distill in order to make vodka than it does to just brew to produce an alcoholic malt.
Where the beverages are sold also contributes a bit to the price. Because spirits are the most controlled alcohol in the country, often you can only find them in liquor stores or state control stores. Fewer outlets selling means there is less price competition. Malts, on the other hand, can be sold almost everywhere — grocery stores, bodegas, gas stations, or big-box chains like Target and Walmart — and that means lower prices as these stores all compete against each other to get you in the door.