You only paid for what the game was when you paid for it. Not for possible future DLC which you had no idea about.
You should have been aware that the project might be abandoned at any given time, as clearly stated by the devs.
I bought 0.21 (~20$) because i was content with it, and couldn't imagine how it can get better. As far as i was concerned, they could ditch the project and i would still be happy, but now i got even more value for my money.
In all honesty, that's all it was worth back then. Only a silly joke about green aliens launching themselves on goofy firecracker rockets.
And again, the project could have ended at that! That's not a game i wanted, and i couldn't predict that it would grow into an absolutely beautiful space flight simulator, could i? which is why i didn't buy it!