If you insist on measuring the economy solely in terms of "substances with intrinsic value" ...

I don't, and specifically pointed out precisely an instance where money was not grounded in material goods. However that is a red herring as money is not wealth but is instead a measure of wealth. My own theory is that the reason many monetary systems have been based on specie or some similar intrinsically valuable material has to do not with coupling/decoupling of production to physical inputs, but to trust. That is, when you have a money-issuing authority imbued with high trust, the need for metal-backed currency disappears. "Seigniorage" is then a measure of trust in the money-issuing authority, and fiat currency (with effectively infinite seniorage) implies complete trust.

(The concern that such authorities occasionally abuse their trust, and/or run up against circumstances in which deflating the currency becomes a financial and economic necessity, is a separate issue. That problem isn't limited to fiat currencies, however, as the devaluation of specie-based currency such as the Roman denarius illustrates.)

The relationship between economic output and material inputs, specifically energy inputs, has been identified by several authors, in particular Steve Keen and Robert U. Ayres, "A Note on the Role of Energy in Production":

Energy plays no role in the standard Cobb-Douglas Production Function (CDPF), and a trivial role in a three-factor CDPF where it is treated as a third input, independent of labour and capital. Starting from an epistemological perspective, we treat energy as an input to both labour and capital, without which production is impossible. We then derive an energy-based CPDF (EBCDPF) in which energy plays a critical role. We argue for the redefinition and measurement of real GDP in terms of exergy. We conclude that the “Solow Residual” measures the contribution of exergy to growth, and that the exponents in the EBCDPF should be based on cross-country comparative data as suggested by Mankiw (1995) rather than the “cost-share theorem”.

<https://www.sciencedirect.com/science/article/abs/pii/S09218...>

As Keen and Ayres note, including energy along with capital and labour in the Cobb-Douglas production function accounts for virtually all of the "Solow Residual", the amount of productivity not accounted for by capital or labour, and which was previously attributed to "total factor productivity". Keen & Ayres reduce that almost entirely to energy input.

Your sojourn into prices as opposed to wealth creation (in the real economic sense, rather than the somewhat more familiar, but irrelevent in this case, financial sense) is yet another red herring. Asset prices are not intrinsically grounded in production costs, particularly for price-inelastic goods such as real estate. Rather than being defined by costs of production, they're defined by surplus value, and following the theory of rents first expressed by David Ricardo, the seller will tend to accrue surplus consumer value of such assets. That is, real estate prices rise to match the income potential of that location.

Information-heavy good such as luxury brands (Apple, Mercedes), entertainment (cinema), are based on a combination of manipulating tastes (advertising and marketing, reputation), constraining supply (particularly in real estate), and in competition for a limited resources (cinema screenings vs. cinema audiences). Note that in the case of cinema, costs of production are independent of viewings, so the industry is very interested in both total budget and ticket sales. But individual ticket prices tend to be relatively uniform across titles, what varies instead are the number of butts in seats. (This varies somewhat: Imax theatres may claim higher prices, but again, this tends to be across all titles, and matinee or off-peak screenings may offer lower prices, but again, uniformly for titles.)

Rice and wheat, as well as oil, gas, and coal, are commodity goods, not assets in the sense of real estate and gold. They're subject to supply and demand, but prices are determined by the marginal or surplus producer, depending on market circumstances. Where demand is less than total production capacity, the surplus producer, that is, the producer who can choose to sell more or less product at will, determines price based on their own production quotas. From 1931--1972, this was the United States, managed through the US Department of Interior (via "certificates of clearance")[1] and the Texas Railroad Commission (through drilling and production quotas)[2]. Since 1973, control has effectively resided with Saudi Arabia, as the US passed domestic peak oil and no longer had surplus production capacity.

Where demand exceeds production capacity, it is the marginal producer of oil, that is, the one whose costs just allow operating profit at the present market price.[3] As market prices rise and fall, those marginal producers enter and leave the market, literally turning on or off well pumps, with the cost of running the pump often dominating their own production costs of their "stripper wells".[4]

Because fuels, and foods, literally power the rest of the economy, as prices for either rise, there is less profitable activity to be undertaken by utilising them. If we express national productivity in terms of $GDP/barrel-oil, there is a range of roughly $300--400 at the low end to ~$3000 at the high end, with the US coming in at about $1,200/bbl of GDP.[5] If oil costs $50/bbl, then that is $1,150 of net productivity per barrel. Should the price rise to $100, the productivity falls to $1,100. The US can afford this reasonably well. A country netting only $250 profit at $50/bbl however falls to $200, or a loss of 25% of economic productivity. (India and China were at about this mark.)

The low price of food and energy masks their true value to the economy, because it is precisely the differential in price and output which is what determines the scale of the rest of the economy. Take away fuels and foods, and you'll find that total productivity falls by far more than the previous total exchange value of those goods.

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Notes:

1. See Daniel Yergin, The Prize, (1992), particularly chapter 13.

2. Yes, the Texas Railroad Commission controlled global production of oil. Because Texas.

3. Or, in cases, not even profit but cover non-fixed costs, and thus encourage the producer to operate at a net loss.

4. See: <https://en.wikipedia.org/wiki/Stripper_well>

5. As of ~2015 when I last looked at this.