If you haven't already, add it to your steam wishlist. You'll get email notification adna push notification if you have the Steam mobile app whenever the game gets a discount.
I find the problem with early access games is they don't follow the usual pattern of release at full price, what a few months if it's too much at launch and watch the price start to come down with each sale. EA games quite often launch at their cheapest as they're released then creep up to parity with similar full releases as they add content.
If you take a look at, for example, Codie's Dirt Rally that went from a strating price of iirc £18'sh and gradually increased with each major patch to £40, discounts excluded. Now you've got the standard wait for it to drop down again. Instead of waiting say 6 months for a full release to drop from 40 to 18 or lower you've now got to wait 18 months for it to rise up and THEN drop.
The good news is that I don't think Reiza plan on keeping AMS in EA all that long and with a new game planned for next year I don't think they'll want to milk this one, the game derserves a bigger userbase.
Another option , if you'd be interested in supporting their DLC plans, is to check out their official forums and buy into the packages they have there that include the base game and what is eesentially a 'season pass'. The price is directly tied to the dollar so depending on your countries strength of currency you may find a good deal with that.