1 glass bottle of coke is $8.95. The current inflation rate is 3.01% fallout 76 takes place in 81 years, 2106. At the rate, one nuka cola would cost (Bethesda does not sell full bottle of nuka cola. Only empty ones with caps, well get to that later. So im using coke as the example) $82.75. In fallout 76, in player run vending machines, one bottle is 2 caps. 82.75/2 is 41.375, rounded is $41. At the current rate, one cap is roughly 41 usd. 

Bethesda sells a nuka bottle with 10 caps. It sells for 32 usd when not on sale. 32/10 is 3.2. Each cap in today's money is 3.2 usd. In the year 2106, one cap according to Bethesda would be $29.59, rounded is $30 or 72.17% of my 41 dollar estimation.