Uncertainty and irreversibility are central to online learning projects, but have been neglected in the existing educational cost-benefit analysis literature. This paper builds some simple illustrative models of the impact of irreversibility and uncertainty, and shows how different types of cost and demand uncertainty can have substantial impacts on investment decisions. The techniques used are drawn from the financial option pricing literature. In some situations uncertainty should lead decision makers to delay projects which would be accepted under the usual rule "invest if the net present value (NPV) is positive," and in other situations it suggests that projects with negative NPVs should be undertaken. The application of one of these models will then be illustrated in relation to a new online course: the Master of Educational Technology offered by the University of British Columbia.