Marxists assert that value derives from the volume of socially necessary labour time exerted in the creation of an object. This value does not relate to price in a simple manner, and the difficulty of the conversion of the mass of values into the actual prices is known as the transformation problem. However, many recent Marxists deny that any problem exists. Marx was not concerned with proving that prices derive from values. In fact, he admonished the other classical political economists (like Ricardo and Smith) for trying to make this proof. Rather, for Marx, price equals the cost of production (capital-cost and labour-costs) plus the average rate of profit. So if the average rate of profit (return on capital investment) is 22% then prices would reflect cost-of-production plus 22%. The perception that there is a transformation problem in Marx stems from the injection of Walrasian equilibrium theory into Marxism where there is no such thing as equilibrium.
For further information consider reading Computer Cleaning Prices