Very Cheap He-3

Due for an overhaul? I'd rather an entire simulated economy.

For example, the extraction and processing of helium-3. An isotope formed in a variety of ways, it can be found anywhere with an active main sequence star. Specifically, there are three sources of helium-3 I'd point to: The surfaces of airless bodies near the Sun, excretions of the Sun and the Sun itself. The first is the simplest way of obtaining helium-3 - just park on Mercury or the Moon - or the gas giants, actually - and scoop it up. The second would involve statite ram scoops or other similar megastructures to collect the Sun's flares directly, cooling them down and sorting hydrogen and helium into tanks as well as any metals. Then there's just taking it directly from the Sun using stellar lifting and artificial stellar mass ejections. That last one is probably unfeasible for this setting, but the first two could be done. Without lifters, using plain solar abundance as a basis for a material's cost is invalid.

Then there's the possibility of producing helium-3 in breeder reactors, though it may be inferior to plain collection.
Gather data using estimations, assign weights to each and you'll have a yearly rate of production in tons. Then multiply that by an estimated cost of production (the sum of all the maintenance and workforce pay per a single ton for each method) and you've got the going rate for each rate. Then add in transportation costs to the area of manufacture, process tax and you've got a figure.

This could lead to a stock and market system that, honestly, could add a whole additional dimension to the game. You could pick a preferred manufacturer, ferry and route to optimize prices for the specific station where you're commissioning new spaceships or simply refueling the old. Synthesizing your fuel in breeder reactors might be cheaper out in the trans-uranian regions than in Mars' orbit, but cheap and tax-exempt, barely-legal shipping might make that moot (though it might take a few decades to arrive, and there's no guarantee half of it will arrive at all.) And that's just the matter of helium and hydrogen production - once you add in manufactured materials like UHMWPE or even plain rubber, the supply chains and markets might get real interesting. But that would only work for a dynamic campaign, wouldn't it?

But for now, adding something as simple as listing all the different factors taken into each cost would be nice. I'd like to know exactly why something costs so much, down to solar abundance and outgassing. Note that these costs aren't really the same, and could vary from container to container - at least raw material costs should be separate from the maintenance and building costs required to store it - in the case of fuel.