It's certainly not that simple, but there are other factors than just whether the new worker generates sufficient new profit to cover his salary. Can the business get by with temporary workers? Can the business make more money by outsourcing some or all work to a cheaper nation? What risks are associated with hiring that new employee? Is the rate of return for the cost of that new hire less than the rate of return for some other use of that money? Would I be better served looking at automation? If I hire this man and have to lay him off in a few months or a year, have I done him a favor, or a disservice? If I hire this man and have to lay him off in a few months or a year, will I even still have that freedom, or will I be forced to pay him (or at east his health care) until he finds other employment? Keep in mind that costs are generally fixed, whereas benefits are an unknown when hiring.
Liberals tend to see the business equation as simple; as long as the employee still produces some profit, we can add cost with him with no effect other than reduced profit for those at the top. In the real world it's not nearly that simple. Jobs don't exist to fund government or provide health care, they exist because someone needs something done and is willing to pay to have it done, and the higher the cost of getting that something done, the greater the chance of deciding that it isn't worth the price after all.