But if no one wanted to spend 30k on it, you wouldn’t be able to sell it either. Demand is certainly a determining factor in the price of an item. Again, it doesn’t matter if it cost you 100k to produce the car. What matters is how many of them there are, and how many of them are wanted (and how badly). That’s it. Supply and demand.
Just because you spent a certain amount making the item and have a desire to make a certain amount of profit, so you set your sale price at a certain amount…that means absolutely nothing to the market value of the item. Just because you set a price doesn’t mean anyone will pay it. Supply and demand determine price…and prices are the objective result of the subjective valuations of individuals in the market. Input labor has absolutely nothing to do with it.
The sooner you let go of “the horizon is flat, and the sun disappears as if going around a corner…therefore the Earth is flat”, the better off you’ll be.