At a higher level of abstraction, having a business that achieves sustainable profits over time entails creating or exploiting market inefficiencies. Perfectly efficient markets generate thin to no profit.Even in neoclassical economics, which assumes perfect markets (money, goods and labor), rent is gain resulting from market inefficiencies. Rent seeking is active exploitation of market inefficiencies.
Thus, it is rational to promote inefficiencies that one can exploit. According to Peter Thiel, entrepreneurs loathe competition and seek monopoly.
It is very difficult to compute rent in that every market that is not perfect, which is all markets. There are knock on effects among markets that amplify rents throughout the system. In addition, externality and transaction cost further complicate the issue since they are not measured.
Rentier activity is a lot like pornography: hard to define in a way you can operationalize, but you know it when you see it.Just as there is soft and hard-core pornography, just as there is economic rent and egregious economic rent.
This conundrum illustrates why almost always a bad idea to try to come up with single point estimates of complex phenomena. If you do attempt to put metrics on them, its better to measure what you can measure reasonably well, paramaterize other important issues as best you can, and make qualitative conclusions.
Oxfam Report on Rent Seeking Among the Top Wealthy Reinforces Neoliberal Shibboleths