You should only be concerned about it if it's your money on the table.
Tim Schafer has cleared up exactly what he was trying to say about game sales not being important. Basically, if it's not your money you shouldn't concern yourself with how many units a particular game sells.
"I think games sales matter a lot," said Schafer. "I just think that the people who should worry about sales are the people who have vested financial interest in a game. If your money or livelihood is dependent on a game, then you should concern yourself with its sales. But if it isn’t, then you should try to relax and just enjoy playing them."
But what if a game you love flops? Does that mean you want see any more game like it?
"I’m saying that’s just not true," explained Schafer. "You’re not hoping for some game that’s superficially like the one you just played, right? What you want is another great game. If a game is a huge hit, yes, there will be a lot of imitators. And those imitators will get green-lit quickly. But those kinds of games are rarely great. So who cares? Who wants that? Great games don’t come from that sort of imitation. They come from people working on an idea they care about."
He concluded: "... as long as you make a GREAT game, people will want to talk to you. That doesn’t mean people will automatically want to publish you. Just that they’ll talk to you."