As much as I wish otherwise, I found an
actual statement from David Braben about that. Like many, I'd missed it at the time, because Frontier's
original timeline was five paid for expansions over a period of ten years.
So their intent
at the time was to go full EA sports with this game, charging AAA prices for yearly upgrades, not matter how minor:
If Frontier had actually kept to this plan, on top of paying $60 for Dangerous and $45 for Horizons, we would've also payed $45 for Horizons 2.4, another $45 for Beyond, $45 for the new player update, $45 for the upcoming Fleet Carriers, and so on. And, of course, and extra $15 each year if you wanted access to the beta.
Needless to say, at some point sanity returned, and they've gone back to their
original plan, which was paid for major expansions, only this time they're releasing it all at once, rather than spreading it out over two years.