I look at this rather differently than the comments above. The .io they have been on (and still are on today) has worked rather well for them. They have grown to 90 offices and 250 employees and have 90 million monthly views across 25 countries.
Yes, the .com is a step up and due to their success on the .io they can afford the $30,000 price tag now. I agree the switch to .com is a smart move, but I don't agree that this is saying anything negative about the .io.
If a startup literally put all of their dollars in year one into a domain, they would not have anything else left for their operation. Just as it makes sense for businesses to start in the physical space they can afford (for many of the world's now biggest companies that was literally a garage or basement) also, at the right time, they move up to the spiffy new corporate headquarters.
Bob