It does not cost nearly as much as the price premium.
A regular household fridge costs something like $100/year to run. My fridge has 20 cubic feet of volume, which is something like 500 liters. This suggests we can fit at least 100 bottles into it. This gives us $1/year as upper bound for storage costs per bottle. This is upper bound, because air conditioning costs go down with volume, due to square-cube law.
Point is, if the price premium was driven mostly by storage costs, it would be significantly lower than it actually is.
A regular household fridge costs something like $100/year to run. My fridge has 20 cubic feet of volume, which is something like 500 liters. This suggests we can fit at least 100 bottles into it. This gives us $1/year as upper bound for storage costs per bottle. This is upper bound, because air conditioning costs go down with volume, due to square-cube law.
Point is, if the price premium was driven mostly by storage costs, it would be significantly lower than it actually is.