When calculating the cost of ownership for eCommerce, you do not factor in costs associated with risk, opportunity cost, or return on investment. These are all important factors, but they are considered separate from the TCO. For example, one option may have a low TCO, but a high risk, and a low return on investment. Even without looking at the opportunity cost you may take that option off the table. In addition, sunk costs are unrecoverable and should never be considered in any financial calculation.