This virtual world is powered by its economy. A vast array of supply and demand. Some companies will rely on other companies and some companies will rely on general population. For example a hospitals and insurance will rely on general population, where manufacturers will rely on importers and wholesalers (and vise versa.)
Worker's in this economy only grow at a set rate, there will only be additional workers to meet a set unemployment rate and only every so often. That encourages wage increases to attempt to steal other company's workers. The challenge is to keep your company balanced so you can stay profitable and keep your employees.
Some workers are industry specific and have more influence in profitiabilty in their respected areas, for example having nurse or doctors on staff of an advertising or legal firm will probably be wasted wages, likewise having salesmen or designers for a hospital may not have a very desirable effect.