Arguments against will be that value "is" what people are willing to pay for them, which is some combination of supply and demand, but I find this just too simple. Technically it's true that the "value" of something is the price someone last paid for it, but then we get situations where we say a Bitcoin is worth 40k usd or whatever tf the price is right now. And then suddenly its value is 20k, and if you ask why you'll get thirty answers, all wrong. Maybe the price was 40k to someone and 20k to someone else, but the value? Nah. And the price alone tells us basically nothing.
The interesting thing for me is the third person. Me, in this case, to whom Bitcoin is worth 0, or less than 0 because I would consider it a labor cost to own a Bitcoin (figuring out a wallet or whatever). How does someone to whom a Bitcoin is worth 40k then then around and say "Bitcoin is worth 40k" to someone like me?
To capitalists trying to nod their heads and say ah the price is high, supply must be down or demand must be up, I say, good luck predicting human behavior, that usually goes great.
For me though I agree with you, the value of goods is some combination of their production costs, in any meaning of the word "value" that matters.
"But what if someone spends an entire lifetime of labor producing a single widget nobody wants? Clearly demand plays a part in value!" I don't know, go away. Why would that happen? Sure, ok, also include in value calculus that hopefully people only make things that people actually want. (the capitalist argument here is, the profit is to be found in the margin between cost to create and the price set by desirability - to which I say exactly, profit should be eliminated)
Edit: someone else had a comment they deleted talking about how profit is necessary so as to have surplus to save in case of equipment failure, I'll paste my response here cause my thumbs put in the labor so by golly I'll get the Payout
Traditionally, are profits sequestered to be used as savings like that? In my experience the equipment breaks and both companies go bankrupt because the executives in the c corp spent the profit on themselves already and are happy to just go find a new investment.
Actually in my experience the other company, the co-op, doesn't go bankrupt, because the workers are smart enough to safeguard their well being with rainy day funds. This might be one of the reasons coops are repeatedly shown to be far more resilient than traditional companies.