I thought it was $70 a month or $1500 flat.
Unity can afford it because Unity IDE and very massively important. Unity came out with the Asset store within a reasonable amount of time. This offered Unity Community to feel confident about using/sharing code. If offered a public convenient repository to access. It offered financial cash flow to smart developers and high quality tools to people who didn't want to re-invent the wheel. The asset store provided everyone a place to help Unity evolve. There are just some user tools that are standard with Unity until Unity team comes out with an official unity version. HoTween, iTween, TK2d, Gestures.... these are so standard. But there are no standardized community tools for C2.
Where as; and as much as a I love C2; C2 is kinda stuck in the dark ages of evolution. People don't have access to quality, many developers re-invent the wheel. The forums great, but as long these community assets are not IDE convenient Unity is going to continue to run circles skyhigh around C2.
I've been calling out for Modularity and an Asset store for almost 2 years. Shortly after getting my license. Haven't seen a single move direction towards it. Instead it's tool improvements that are needed, but none of which will evolve C2 as the tool to use.
And Squidster is right. Scirra has been looking for employees. But havent' found any in two years. There aren't enough of them. If Scirra had 5 employees and 4 of them were programmers you would see massive amounts of work go into C2. Far faster than what is currently happening. Supposedly they are making enough with just the sales. But they would get a better revenue stream if they had an asset store.
So. yeah. that's why,