Standard, modular drives
The drive blocks used by 90% of all small-to-medium spacecraft are all standard, mass-manufactured and cheap. You can find replacement parts or whole drives on every station, no matter how far. People use them in case they break down or melt far away from major civilization, most don't want to risk getting stuck on some asteroid mining colony because their drive broke down. So, they go with what's easily procurable everywhere.
Now for the rest of the ship, sure there are some big corporations that produce shiny, premium feel™ assembly line iShips, but those, even if they have nice features and trinkets built in, are usually way overpriced, don't allow for any customization and offer no significant performance boosts over the other kind:
Open source, garage-built hulls. Plenty of low budget entrepreneurs set up minidocks in their space-garages, get a good foundry 3D printer, some assembler bots and design and build perfectly usable ships at affordable prices. Some kids who are just starting out might be willing to build something for you just for the price of materials. They'll even hack the regulators and overclock your drive so you'll run circles around the rich kids with their shiny toys that cost 30x more. No guarantees on stability though. Or any guarantees at all.
A shadow economy
Ships are very expensive, but in this age spaceflight technology is advancing at a rapid pace, so any company, to stay competitive, must throw unholy amounts of funds on research. To get those funds it must sell as many ships it can, as often as it can, at the highest price it can.
So we get planned obsolescence. Not only is the average journey time is decreasing by 20% every five years, but all the other tech like sensors, life support, comms, inertial dampening, etc is advancing at such a rapid pace that owners are forced to change out their ships every 5-7 years to stay competitive themselves.
And they do. 500
The rich ones living in the central sector, working the major commercial routes, that is. That's not for us, though. We're far out of the way, nobody every comes here from Central. No shipping routes from the delivery giants, there's no profit for them here. They keep to the commerce sector where business is fast and money flows in rivers.
And that's true for everyone living on the periphery, the edges of human civilization, save for some important commercial hubs. Even if we outnumber the central sector inhabitants, they have vastly more money than us. So much more that our economies aren't even compatible. We'd need to get our whole colony to save up for a year just to get 1 new ship.
We get our hands on the "old" ones instead. They scrap the outdated models, sometimes recycling them to build new ships, but usually just store them in some orbit. They aren't designed to last, build quality is fairly cheap, but we can still salvage them. Reinforce the hulls, swap out some of the new flimsy, gimmicky systems for the older, more robust kind, customize any additions we might need, like freight hauling modules or passenger blocks, and we have perfectly usable ships.
Not the fastest in the galaxy, but enough to get by, get the mail delivered. We supply all of the periphery with ships they need to survive, to trade, to continue expanding the reach of humanity. 500