There is a price for labor, which is the market price, and there is a price for capital, which is an interest rate. Firm ownership is an arbitrary thing that can't be reduced to some kind of initial labor or risk. It is the ownership in perpetuity of all the surplus of a firm. Nothing is unique about capital being advanced, there are classes of loans with risk premiums that attempt to price the risk involved. There is nothing unique about doing R&D or market research, many people are paid a salary for it. It's just arbitrary, even within the logic of liberalism. There is a contract that is allowed which says you can own all the surpluses of the labor and capital owned by a firm, owned by you as your property. Nothing in particular justifies this, it is just a social fact, like the outright ownership of a person's labor for the duration of their life was at one time a legally sanctioned contract.