Remedy Entertainment has announced today that starting tomorrow, May 13th Alan Wake will be on sale for 90% off on Steam. The reasoning behind this sale is that there will be expiring music licenses. Users will have until May 15th to purchase Alan Wake on all stores the company stated and in case you were wondering if you already own the game before it is taken down from stores you will still be able to play it.

NO! Only from the Steam store.If you own the game, obviously, you can keep playing it.

— Remedy Entertainment (@remedygames) May 12, 2017

Here are all the question and answers Remedy put up on their forums:
What exactly is being discounted
The Alan Wake Franchise including Alan Wake, all DLC, Alan Wake’s American Nightmare
Will you bring Alan Wake back to stores?
We are looking into relicensing the music for Alan Wake, but have no timeframe for this.
What happens to Alan Wake’s American Nightmare / Will other Alan Wake SKU’s also disappear?
Alan Wake’s American Nightmare will remain in stores. Remedy negotiated the music licensing for Alan Wake’s American Nightmare, we did not negotiate the licensing for Alan Wake’s licensed music.
Why does the discount differ in some stores?
Remedy and Microsoft cannot control how individual stores want to price the game. We can only control pricing on Steam and Xbox Store.