Well, that parrots Marxist dogma, but it is false in theory and usually in practice. The price of labor, like the prices of everything else traded in a free market, is determined by the law of supply and demand. Employers pay what they must, but no more than they must, to obtain workers with the skills they need --- just as they pay for everything else they buy (and just as you pay for the the things you buy). That means employers cannot arbitrarily set wages, any more than they can set the prices of the steel or energy they must buy. If they offer less than the prevailing market rate for a particular skill set, they will have few or no takers. If they offer much more than that rate, they'll be forced to raise prices on their products, and become uncompetitive.
That dogma is vacuous for two reasons. First, it is anachronistic, in that it views "labor" as essentially unskilled muscle power, of the supply of which, in modern economies, far exceeds the demand, and whose market value is therefore low. Most workers today are not selling muscle power; they're selling a wide variety of skills. "Workers" embraces everyone from research chemists at drug companies to professors at universities to physicians at HMOs to corporate lawyers to bank lending officers to cops to car salesmen to journeyman plumbers to airline pilots to burger flippers at MacDonalds. Employers have little control over any of their wages.
The second problem with the dogma is that it rests on an unfounded, spurious moral assumption: That employers have some paternalistic responsibility for the welfare of their employees, which entails a duty to pay them a certain minimum wage (a "living wage") and provide them with various benefits.
They have no such duty. No person has any unassumed, a priori duty to promote the welfare of any other person. One acquires duties to others only by taking some action --- by entering into a contract or making a promise, or by bringing a child into the world, or by injuring someone, thereby incurring an obligation to pay damages.
But of course, if you insist employers have such duties, then some moral argument for the origins and basis of that duty will be required.
If a worker is unsatisfied with the wage or salary his employer is paying, it is his responsibility to acquire a new skill set, one better rewarded in the market. The employer is not his father, rich uncle, or guardian angel. The personal welfare of his employees is not his concern, except to the extent it affects their ability to do the work for which they were hired --- any more than the welfare of the owner of the store where you buy your groceries is your concern. Your interests and his coincide at the point of sale, and your relationship extends no further. You have no obligations to one another other than those implicit in that transaction.
(more later)