The mindset to pay that much for a vehicle in a game seems crazy to me.
Slightly off-topic, I find it hard to think of this in terms of "crowdfunded backing" as we have come to understood it from Kickstarters.
Looking at how each of these purchases is actually buying an in-game vehicle (and not peripherals or other merchandise), I'd file a large portion of those 50 million dollars under "revenue made from in-game purchases" instead of "development money raised via backers".
Not sure if that distinction actually makes any functional sense, it does in my head.
I would call the purchasers backers, since this ship purchase system was designed to boost pre-launch income and will cease to exist or at least be significantly modified when the game is finished.