From Astro Wars
Astro Dollars are the Universal Currency in Astrowars. Astro Dollars can be attained through Trade by selling Production Points (PP) or Artifacts or Supply Units (SU). Astro Dollars can also be gained if you attack and destroy a defending fleet at an unknown Planet, but the random chance to find some money there is low.
Astro Dollars are needed in Astrowars to purchase such items as Artifacts, Supply Units, and Production Points. Astro Dollars are also required to initially set up a registered Alliance, and to contract Trade Agreements with other players.
Selling Production Points to get Astro Dollars via Interstellar Trade.
At this trade screen you can see what Astro Dollars are worth.
Astro Dollars, as with any currency, will fluctuate in value by a small amount. This can be seen in the Trade Screen which shows current as well as past values so possible patterns may be analysed. The values are updated at each Daily Update.