If you are picking a barrel of Knob Creek, not at the distillery, they send a kit with barrel proof samples from 3 barrels, distillery water with a graduated beaker and a chart to equalize proofs if you choose, and a chart that shows exactly where in the rickhouse the barrel is resting.
Even the location in the rickhouse has a significant impact on the aging process. Barrels higher up and closer to the walls are exposed to greater ranges of temperature, altering and accelerating the aging process. Barrels are not airtight, air and water molecules being smaller can more easily escape than alcohol molecules. Changes in temperature and barometric pressure move the whiskey in and out of the wood, where it extracts flavors.
Barrels on a ship at sea are typically exposed to the sea air, greater changes in their environment, and the major factor of motion. Sloshing around in the barrel exposes the whiskey to the wood more quickly and evenly and is generally considered to accelerate the aging process.
Jefferson’s Oceans releases are by voyage. Individual barrels from the same voyage will still have differences, sometimes very significant.
Whiskey pricing varies due to a number of factors, including supply. A bottle in high demand, say Blantons, will command premium prices on the secondary markets even if they are not as “good” as other bottles where demand is lower relative to supply.
I’ll admit I’ve never tasted a Jefferson’s Ocean that compared to that single barrel pick of wheated bourbon from Voyage 19, but your mileage may vary.
A friend gave me a pour from a single barrel of Glen Grant last night, 34 years old, and it was amazing, rich and dense and smooth, but it cost hundreds of dollars a bottle. On the other hand, I could point you at a dozen bottles of bourbon at $50 or less that I think are superior to bottles costing 3-4 times as much.
There are certainly better and worse whiskeys by objective measures. We once had seven tasters from our bourbon crew pick the same barrel from a group of seven barrels of New Riff in a blind tasting. But palate preferences are highly individual. For example, I tend to like wheated bourbons. Heavy oak and double oaked bourbons, not so much. I like some scotches, but heavily peated scotches, not so much. But that is taste, not quality.
Don’t measure whiskey only by the price. If the only bottle I could ever have was Rebel Small Batch Reserve I would be content, and it’s $30 a bottle.