How to evaluate the value of non-patented technology

The evaluation of technology value is flexible, and it is difficult for others to help you without a clear explanation.

Suppose he is not here, you can earn 1W a year, because he (who knows technology) is here, so you can earn 1W, and his technical value is 9W. If his salary (paid technical value) is 4W, his contribution is 5W/ year.