Look at the Amazon SDEs income statistics at the location you’re being hired to. Evaluate your current level of expertise and aim to the top 80% of the distribution.
While negotiating an offer, don’t tell them your current salary, you can tell that it’s confidential or some policies forbid you to share it.
Tell them you have an offer from Microsoft (or other known company). Be specific — mention expertise level, benefits breakdown, team and role. You can find a lot of data about roles and terms used at other companies to, make it look realistic based on your current conditions.
That’s what I did.