We use the metric system. Milk comes in 1 liter packages. It's around 4 liters in one gallon. The price is about NOK 12 which is about $2. Bread varies a lot in price, from NOK 5 to NOK 30 or more for special bread types. The cost of living is very high here. Wages are high, taxes are high, everything is high.
Petrol, diesel, tobacco and alcohol are super mega expensive due to a number of extra taxes.
A bottle (0.7 liter) of whiskey cost about NOK 300-500 depending on quality. One liter of petrol is NOK 13.25 at the moment, it has been more than 14.
If 1 gallon is 4 liters, it's NOK 13.25 x 4 = NOK 53.00 for one gallon. These days one US dollar goes for 6 NOK. This means I pay $8.83 per gallon. It's not completely accurate because one gallon is not exactly four liters.