The problem is thus: How to price every good and service at equilibrium in the economy, with regards to the marginal cost and marginal benefit of every individual for every good and service.

You have not seen any suggestion to solve this problem, does not mean it isn't NP-hard.

>> we just might not have to computing power to calculate it.

There is a perfect answer, and there will almost never be enough computing power to calculate it. It is always approximated.

Keywords being cost, benefit and every individual. Those are all big variables. Everybody will define what the cost and what the benefit of everything is differently, both from their own perspective and from the perspective they perceive that others has/should have.

So you'll have more "perfect" answers than people, and no way to select any one of them.

That's like saying if you don't have a GPS the travelling salesmen problem isn't at least NP complete because you don't know what the weights are and every edge has a different weight, which would screw with your calculations.

It's not a valid argument against the fact that everyone does have their marginal benefit and marginal costs for every good and service that can translate to a binary decision of whether they would purchase a good or service at a given price.

Just because you can't see it doesn't mean it's not there. And I'm not saying it's impossible to find out individuals marginal benefits and costs, because in markets you very well can. Stock traders, when evaluating whether a stock would go up or down, would often buy a bunch of stock, see how the market takes it, then sell a bunch, and by measuring how fast the market eats his orders, he can estimate the aggregate marginal benefit and cost of holding the stock, and then speculate accordingly.

> the fact that everyone does have their marginal benefit and marginal costs for every good and service that can translate to a binary decision of whether they would purchase a good or service at a given price.

I think this fact is more like an axiom.

An easy way to check if you have an NP-hard problem: If I give you the right answer, can I easily convince you that the answer is right?

With NP-hard problems like Sudoku, that's easy. Slightly simplifying, the definition of NP-hard is "easy to check the answer, hard to find it".