Microsoft helped price his skills, and their value will surely not diminish in three years. So, it is more like putting off the opportunity of making $300,000 now by three years. Having accepted the offer now could have made him more risk averse three years down the line (in the face of a more tangible opportunity cost in terms of lost paychecks).
In fact, it is a very rational choice if your window for evaluating expected outcomes is five years or more.
