Space Dandy is a different case though. Wasn't it partially funded by Adult Swim/Toonami? I imagine it doing well over here was pretty important for that show.
It was. Originally it was only supposed to be 12 episodes, but once DeMarco and the others threw money at them it was expanded to 24. I imagine success over here matters quite a bit for Dandy, as it was partially funded by AdultSwim/Toonami.
Space Dandy, according to this person who takes the time to collect sales data, sold around 1,000 units.
It's not a total view of sales data, but it's save to say Space Dandy probably wasn't a success financially.
But it was never meant to be. It was a series made because the people behind it, loved it.
Due to the way it was funded, you probably have to look at more than just the Japanese market.