Ofcourse the amount of labor is important, but the price of a good is determined by the subjective valuation of individuals. The value is not determined by the amount of labor put in it. And that is what the labor theory of value states. I have put so many hours in this product so it must have value. It doesn't work like that. But central planners decide to produce goods with lots of labor and resources and think it has value. It leads to huge misallocation of resources and labor, because in communism you don't have the feedback loop of subjective valuation through the pricing mechanism they don't know what to produce in which amounts. You can not do economic calculations without prices.