Shipping things back to Earth is almost certainly how the Homestead Corporation makes money
We are told that the Homestead Corporation financing the trips is a for-profit company. Previous trips to the planet Homestead were extremely profitable, so much so that they invested heavily in Homestead II, which is where the Avalon is headed.
Consider the fact that after the ships are launched, the Homestead Corporation back on Earth doesn't have any way to make money off of the trip unless something is sent back. How would it be sent back?
- Digitally (e.g. scientific information, video footage)
- Physically (e.g. raw materials that are rare or unseen on Earth)
We know that passengers have thus far not returned physically, so that means that they are making their money either off of the digital data that is being sent back or the stuff that is physically sent back.
Personally, I don't think that scientific information or other digital data would be all that valuable. In our modern day, NASA and other space agencies regularly collect scientific data, and although it is useful for a number of things, it's not particularly profitable (which is why such agencies are government-funded). Private space companies make their money in either deliveries or passenger trips.
Since passenger trips aren't what's happening here, I'd wager that sending back raw materials, especially if there are useful ones that are not found on Earth, would be worth far more than any digital data would be. There is also the possibility that other planets contain useful materials not found on Earth, (cf. unobtanium in the 2009 film Avatar). Imagine how much an Avalon-sized ship of useful precious metals would be worth if they can't be found on Earth?
Given this, I submit that the Homestead Corporation regularly sends raw materials back to Earth in cargo ships, from which they make their money. Aurora would be given a hibernation pod on one of these cargo ships filled with raw materials. It likely would not be as nice as the Avalon, but it would get the job done. While the cargo space needed to support her would be able to be used for raw materials, I imagine that there would be a considerable amount of good PR that would make it worth it to the company.
A deleted scene indicates that the Avalon has been used for multiple trips, so obsolence is not an issue
Addressing your concern about what people back on Earth would do with a 240-year-old spaceship, it seems that the Avalon has already had a long life.
The Avalon's made five interstellar trips, I've made all five of them. I've never seen anything more serious than a burnt piece of toast, and now this…
While "insterstellar" could also mean relatively short trips, like Earth to Alpha Centauri (~4.37 lightyears away), the point is that the Avalon is already a ship that is used for years and still is modern enough to be used as a colony ship to the farthest reaches of space.
Additonally, the original script had Gus comment that one of the ship's CPUs was rated for 500 years.
Passengers: Original Script