

something is worth whatever somebody is willing to pay for it
That’s a naive short-term approach to valuation.
Real value has to be measured in some kind of revenue generation, or - at least - cost mitigation. Otherwise what you’re describing isn’t value but expense.
the willing buyer is the key to the whole valuation equation
The willing buyer is the key to perceived value. But suckering someone doesn’t increase the utility of what you sold them.
Except credit changes the math on that significantly. You aren’t constrained by your income, but by your risk of default (and even then… glances 2008-ward) Then you can afford to buy more by paying a higher interest rate.
“Willingly” is doing a lot of lifting, given the degree to which fraud, extortion, and price gouging play a roll in the national economy.
Promotion (and deception and intimidation) drives sales. They create the illusion of scarcity and transform luxury into necessity.
They add perceived value among the unwitting and create implicit value through absence of harm.