They'll be comparing the instantaneous value of the stock with the value of the raise. So if you previously got pay for the month of let's say $2,000 plus $400

They'll be comparing the instantaneous value of the stock with the value of the raise. So if you previously got pay for the month of let's say $2,000 plus $400 in RSUs (the value of the RSUs at the moment they're assigned), then you might lose the RSUs but get paid $2,500 per month -- a $100/month raise. If you then feel that Amazon stock is a good investment, you can buy $400 of Amazon stock on the public market, and you'll be where you were before, plus $100 in cash.