I didn't make any such assumption. I just said that if you only cover R&D on success and fail to cover typical failures, people won't have an economic incentive for doing R&D.

In fact the returns are higher than the necessary costs, including the costs of the failures. That is one of the reasons that pharma is profitable.

However what this also means is that big pharma lobbies hard for long patent terms. And when they get them, then other fields, such as software, have to put up with them.