Hypothetically
Whisky and similar spirits are distilled in an alembic still, google it, they’re cheap.
Vodka is distilled in a reflux still which produces a much purer product because it returns more of the crap back to the still.
You need to keep the whisky in toasted (carbonised) barrels for years to absorb a lot of the crap that vodka distilling leaves behind in the first place. Which is one of the reasons why small stills are uneconomical, you need to have enough product in year 10 to sell and pay off the investment and 10 years of costs.
Gin is vodka distilled for a second time in an alembic still with botanicals. Which is why its popular with hipster distillers as there is a relatively low barrier to entry and it’s easy to come up with a unique recipie.
Whiskey, whisky, bourbon and rye all start off with something recogniseable as beer (vodca can too, but you can also make it from table sugar as most of the flavour is stripped out later anyway), so on top of the still you have the aded cost of a brewery (although on a small comercial distillery scale I suspect getting your beer contract brewed is cheaper).