What do Abundant Luxuries actually do?

Solution 1:

Reducing the buyout cost means that, when you rush-build an improvement or ship, it will cost you less Dust. Thus, it's only valuable if you're going to be buying a lot of things in that system.

Is this system near the front lines of a war, and you're going to buy a large number of ships at it? Is this a brand-new system, and you've decided to rush-build most of the system improvements it needs? Do you have gobs of Dust lying around and nothing better to spend it on?

If you answered "yes" to one of the above questions, then this improvement is useful to you. If you're just rush-improving a colony, then you'll be better off dismantling Abundant Luxuries after you're done improving it, so that you don't have to pay its maintenance cost. If it's one of your major shipyards, keep it around for the next war. In all cases, if you don't keep enough Dust around to rush-build things, then don't build this improvement.

Solution 2:

The "buyout cost" is the cost to press the coin symbol and rush a production. Subtracting out 1/5th of those large costs can save you money in the long run, especially if you have planets devoted to churning out fleets.