Extreme luxury, without the need to worry about most needs. Can live a lavish lifestyle with society’s elite. May own multiple houses, boats, cars, and luxury vehicles and goods that convey a sense of superior status.
Nathan.Dowdell said Jun 21, 2015
As much as anything, it's a reflection of variable prices from different vendors, haggling, discounts, ability to get things on credit, the cost of licences, and so forth. Like a damage roll, it's a reflection of the myriad variables involved in the process - the speed and weight of different bullets in a magazine don't vary that much, but those aren't the only factors in a damage roll.
The system doesn't strictly reflect walking into a shop and handing over cash. It reflects deciding to buy something looking for the best available deal (hence why Momentum on the Lifestyle test can reduce Cost - you find a better deal), which can take anything from hours to weeks. The basic test, and the uncertainty is a matter of risk - you're seeing if you can find an item of whatever type that you can afford in the shortest possible time. Sometimes, you can't find one within your price range in the time you've got. Sometimes, you might spend longer looking for something (as per the difficulties table in the Skills chapter) to gain extra Momentum to spend on reducing the Cost, representing shopping around for a discount.
Your example doesn't really line up; whatever the roll, you can spend Assets to make up the shortfall, so it's only with expensive items you're likely to find yourself unable to buy at all, and vehicles tend to vary a fair bit in Cost.
Also remember that a good portion of the Mutant Chronicles setting is as much feudal as capitalist, and even in Capitol, being powerful and influential can mean you get a lot of things free or cheap that other people pay a fortune for (for a real-world example, consider athletes getting free stuff from their sponsors, or celebrity endorsements of products).
Game Development - 2D20 System
Lead Writer - Brotherhood Sourcebook for Mutant Chronicles 3rd Edition