Alchemy of Accumulation: ratial trait or empire passive tied to tier 1 tech:

-If you have at least 1000 Dust, reduce the cost of your first buyout this turn by 10% of your current Dust. Increase the multiplier based on the amount of Dust you own.

-Multiplier increases by 5% each time you double the base floor of 1000 dust (2000, 4000, 8000, etc).

This is lore friendly in the sense that Dust is basically magic and can have properties beyond being a stand-in for 4X money. It makes the resource more useful to collect early on while encouraging measured use (save up for the next discount tier vs saving crucial time). Being able to buyout some buildings is great for expansionist play, but expansionists tend not to have a lot of money.

Some math on the discount: I chose logarithmic (base two) growth because it scales meaningfully in the earlygame, and then slows down enough to not totally break the economy later. A 60% discount would require over a million dust, for example. The full hundred percent would require over a quarter billion, and at that point the economy is likely thoroughly exploited anyway (and it's only one buyout per turn).