Put simply, economic PPPs are those that offer a potentially viable return for investors. The market price for these assets or services exceeds the cost of operating them, leaving adequate returns for private-sector investors or funds for re-investment in the assets. In other words, economic PPPs are those that are meant to be financially sustainable, and in which the returns on investment are largely financial in nature. A privately-funded, government-supported toll road is a prototypical example of an economic PPP, because the market tariffs-the tolls paid by drivers-exceed the cost of operating the road.