you really have no clue about purchasing power.....
lets look at the 1880's, the "wild west" era, as its the style for the setting. at that point the richest man in america was the railroad modul William Vanderbilt.
he had a total net worth of just under $200 million dollars. (roughly 4 billion in today's money)
the census of 1880 reported that the average income of a working man was about $116 per year.
that's the *average* income.
So, we have the richest, with a total wealth of 200 million in 1880, and the average person who makes about $120.
At the same time, the cost to travel from Southampton to New York by steamer ship as a transatlantic voyage in steerage (the cheapest travel, effectively 3rd class, in a cargo hold, with no access to decks, fresh air etc) was about $30. (£6, when the exchange rate was $4.40 to the pound)
So, it can be concluded, 1880's setting, the cost of travel for the average earning american for a major voyage to an entirely new location would equate to roughly 1/4 of their annual income, or put another way, 3 entire months' pay, not considering the everyday costs of food, rent, etc, that they would need to pay out to live. It would therefore be accurate to say that the average income individual would expect to take 6 months or more to scrape the cost of a voyage if they sacrificed much of their living conditions and were as frugal as possible.
If we transfer that to our sci-fi setting then if the richest are billion or trillionaires, we can safely assume that the average income is the aforementioned $50,000 - but modern incomes are var higher per hour in terms of purchasing worth - so if we extrapolate that, instead of 1/4 of an annual income, the cost is half an annual income, we get a more representative figure. If space travel is a mature technology similar to the liner in the 1880s, it in turn can be equated that a voyage in the crudest, locked-in-a-cargo canister class of travel is going to cost $25,000