If you don't plan on making acquisition of riches an important part of your campaign and thus can live with a simplified player economy, here is a system I cobbled together:
Both prices and wealth are only tracked on a exponential scale as orders of magnitude (With steps of 1$, 10$, 100$, 1000$, 10.000$ and 100.000$ in my case, but for a galactic economy, you might want to push the scale higher), where the value that is associated with a certain level of wealth is equal to the kind of purchase that you mull over a lot when offered, because it might drag down your budget.
For example, take a middle class household. For them, a holiday in Australia would probably be considered borderline -- they might afford it once, but certainly not every year. The money needed for that is several thousand per person, thus, we can define that middle class household to correspond to the wealth of 1000$, because that's the kind of purchase that is borderline for them.
If somebody buys something with a price below their wealth level, their wealth doesn't go down (unless it's a bulk purchase of sufficient magnitude to bump it up some levels). Buying a meal (1$-level unless you're going to a fancy restaurant) doesn't affect how rich somebody is, usually, and this way we don't need bookkeeping over those tiny purchases.
If somebody buys something of the same price as their wealth level (e.g. the flight to Australia mentioned above), they roll a die and have a chance to drop one level in wealth (I set that chance to 30%, so you can make about three purchases of your wealth level before you're broke).
If somebody buys above their wealth level, they drop one level automatically, and still have to roll the die for possibly a second drop. For each further level above their own, that wealth loss doubles. If that wealth loss exceeds their ability to drop (You can't drop below 1$ wealth), then the purchase just doesn't happen.
The assumption here is that what this drop in wealth represents can be many things. Maybe you had to just access your savings account and now it's empty and you need to save again before being able to spend big. Maybe you took out a loan. Maybe you sold some property to afford it, and now need to save to buy that again.
To move up in wealth level, a character needs to get a profit of a level above their own (so for example a 10.000$ profit for the 1000$ middle class household), and then gets to roll a die to move up (I set the chance to go down with wealth level, by requiring a roll under 4 on a D4 to D12 depending on level, but you can change that if you consider that a depressing model of social mobility). Profits two or more levels above their wealth means one automatic step up the scale.
This system allows me to very easily make up the prices of things when the players want to buy, by using one of the following heuristics:
- Do I consider that purchase and the possible threat of poverty for the heroes to be interesting in terms of plot? If not, then it's somewhere below their wealth level and can be ignored.
- Where would I put the Earth equivalent in terms of price category? A personal spaceship in Star Wars seems to be rarer than having a car on Earth, so since a car is a high-end middle-class purchase (Meaning I'd peg it as 1000$ for a used car and 10.000$ for a new one), a spaceship is probably a 10.000$ purchase, or 100.000$ if you want a luxury one.
- How rich is the person making it? This one works better in a pre-industrial setting, but still: Since wealth is tied to income, and income gained by selling things, you can in return determine the price of things from the wealth of its maker, or in case of services, from the service provider. So a slave, being poor, is probably not going to be expensive, but hiring a renowned bounty hunter, who own their own ship, should probably costs in that same range as the spaceship.