They sold 1.1 million copies in its first two weeks, and around 2 million copies in total.
Compared to Sim city 3k/4k, that is less than half the sale numbers in a growing industry. I would also guess that Sim city 2013 had a much higher production cost, server costs, administration cost and support costs.
And most wonderful thing, they can't blame pirates.
Worse for them - though they'll continue to have some new sales, the initial spike is over, and the costs of maintaining their online infrastructure will continue to eat into any sales revenue for as long as they keep it active.
Makes you wonder how big a margin there is between sales revenue and ongoing costs.
I believe that they used online mode as an excuse to limit reviewers to only be able to play for 8 hours, so many of the limits were not apparent.
The game really only starts showing it's shallowness once you filled up one city space and started on your next one, only to come out with a homogeneous clone of the first city.
I know I bought it because the articles about the game failed to mention the size issues or any of the faulty AI issues (like traffic). I was amazed the reviewers didn't find any of those faults because they happened pretty fast and ruined the game for me.
Offline or not, Simcity was a huge step back for me and not worth all the hype it got.