Uh...
You're saying that there's a theoretical line above which films are successes and below which films are flops. That's not how it works. You need to take multiple factors into account.
Ex Machina might be low grossing, but it's not a flop, nor was it a disappointing result. $25m for a platform release of a very cerebral science fiction film from a small studio and a limited marketing outlay is fantastic. It was 60% higher than Spring Breakers, which got a lot more pre-release buzz.
District 9 has a much more conventional approach, a lot of action to sell it, and had a major marketing campaign.
If you want a better 2009 comparison, look at Moon. Small budget, cerebral sci-fi that had good reviews. And it did okay, but was a bit disappointing in that they never gave it any awards push. So Ex Machina's looking a lot better.