Obviously you can’t have an objective standard of value, because every thing bought or sold (or not bought or not sold) is merely based on someone’s subjective whims.
Take, say, coffee. Is a cup of coffee always supposed to be a dollar? But what if there’s a coffee blight, and the supply of coffee is cut in half? Should we still mandate that a cup of coffee costs a dollar? What if coffee farmers increase production, and there’s twice as much coffee supply as before? What if people stop drinking so much coffee and switch to tea? What if there’s a craze for coffee houses and people start drinking a lot more coffee? What if I produce inferior quality coffee beans, and the farmer next to be starts growing better tasting beans? What if I serve watered-down sludge, and the cafe next door serves handcrafted espressos?
Obviously there can never be a decree that a cup of coffee will always cost a dollar, no matter what. Even if you can take a dollar today and go and buy yourself a cup of coffee, there’s no guarantee what the price of a cup of coffee will be tomorrow, or next year, or 20 years, or 100 years. It is ridiculous to expect, given the changes over the last 100 years about how coffee is grown, shipped, processed and served that the price today should be exactly the same as the price 100 years ago. And this is true regardless of whether we use the dollar, or the pound, or the yen, or grams of gold, or bushels of wheat, or cowrie shells as the unit of account.
It is perfectly possible for a business to keep their accounts, not in dollars, but in some other currency. You could buy and sell for dollars, but every time you make a purchase you calculate how much gold that would have taken, and every sale you calculate how much gold that earns. All your assets and liabilities can be tracked in grams of gold rather than dollars. The only defect of this system is the constantly changing value of the dollar relative to gold. Sometimes gold is high, sometimes it’s low. If you have a store are you going to raise prices in dollars every time gold is high, and cut prices when gold is low?
What would be the purpose of that? What exactly is the purpose of money? Money is a good that can be used as a medium of exchange, a store of value, and a unit of account. Again, you can use any good as money, but some goods are difficult and annoying to use as money, others are easy and convenient. So in Africa cows were used as a form of money. You would buy and sell land in terms of 100 cows for this farm, or 15 cows for that farm, or whatever. But cows are a terrible form of money, because they need to be constantly fed, they vary in quality, they die, they’re large, they’re difficult to move. And so of course, since ancient times people realized that small bits of precious metals were very useful as money. Gold and silver don’t evaporate or die, you can set them on a shelf and decades later they’re still there, they can be divided into arbitrarily large or small amounts, they can vary in purity but that purity can be objectively measured, they are small and portable relative to value, and so on.
And so gold and silver were frequently used as money. But the problem is that actually exchanging ingots of gold and silver is less convenient than exchanging the idea of gold and silver. If you come to my store and buy a bushel of wheat, you could give me a silver ingot of a weight that we both agree is equal in value to the weight of wheat. Or you don’t actually have to hand me the ingot, I can just write in my ledger that you owe me such and such silver, and you agree that you owe me such and such silver. No actual disks of silver moves, just the idea moves.
And now what have we invented? Fiat money. The idea that you owe me a certain value, tied to nothing except what we agree on. It’s easy to see that if tomorrow there’s a grain blight, I’ll wish I had kept the grain I sold you because it’s now worth more than the silver. If tomorrow a ship stuffed with silver arrives from Peru, then I’ll wish I had kept the grain. If tomorrow a ship stuffed with grain arrives from Egypt, what then? Of course every price of every good and service on planet Earth fluctuates relative to the value of every other good and service, this is easy to see with just two commodities like silver and wheat, now factor in the millions of goods and services produced and consumed on Earth every day, and you’ll see that there’s no way to have an objective valuation of those goods, let alone an objective valuation that stays stable over years or decades.
Yes it’s true that with 2% inflation the value of goods and services relative to the unit of account drops by half over 35 years. Which means that you can’t easily compare prices over the decades or centuries. But people don’t lose 2% of their wealth every year, and half their wealth over 35 years, unless they metaphorically put all their money under a mattress and leave it there. Except most people’s wealth doesn’t consist of stacks of banknotes in a vault. The only people where this is true are people with almost no net worth, you might have a wallet full of cash but that’s all you have, and it will all be spent by the end of the month.
It’s ridiculous to expect that since you bought a TV in 1985 for $200, you should be able to sell the TV today for $200. That if you had $200 in 1985 you should be able to purchase the exact same basket of goods in 2016, because $200 is $200. That could never happen. So why would you expect that since you could buy a candy bar for $0.50 in 1985 you should be able to buy a candy bar for $0.50 in 2016?
A dollar is just another good, and it follows the exact same laws of supply and demand as other goods. Yes, the value of a dollar isn’t stable over the decades. Neither are the values of other goods, including gold. A dollar doesn’t have an intrinsic objective stable value, neither do other goods. The price of a bushel of wheat relative to a dollar, or a gram of gold, or nice shirt, or an acre of land isn’t constant over time, and to expect these values to stay the same is delusional.
So what that a dollar doesn’t retain it’s value? Yes, high inflation, like 10% annual inflation, is annoying to deal with, and requires all sorts of annoying accounting. Really high inflation, like 100% annual inflation, is really annoying to deal with. Except right now we have something like 1% inflation, or maybe 2%. That means the dollar is very useful as a unit of account for the timescales most businesses are interested in, this year and maybe the next few years. The value might be different 30 years from now, or 30 years ago, but that’s not super important as long as the value isn’t going to change in unexpected ways tomorrow or next year. That makes it safe to keep dollars in a bank account for a year without worrying that next year the dollar will be wastepaper. It doesn’t matter that 100 years from now you won’t be able to buy a cup of coffee with that dollar you put in the bank back in 2016, because that’s not what a dollar is for.