Its damned near impossible to separate out all the component costs of what it took to get SC to where it is now, with that Rock Star spent $200 to $300 Million on marketing.
Unless you know exactly how much CIG spent on marketing you don't know what the raw development cost is.
Lets do some quick maths, CIG have been a fully fledged developer for about 6 years, during that time they have had 500 to now 700 devs, so 600 average, average salery $30,000, $18m a year, X 6 years = $108m just on staff wages.
Well, if you believe CIG, as apparently you do, at least 350 million has gone towards development.
Although what they class as going drectly to the game's development means might not match what others think. It certainly paid for all those hollywood actors to come in and do mocap and voice acting. Do they consider money spent on marketing as going directly to the game's development? One would assume not.... but... where do they get the marketing money from then, which runs to at least a few hundred thousand per year IIRC. Subscriptions? That would be funny. Subscriptions paying for the game to be marketed, although, we "know" that they do, because CIG actually said subscriptions pay for things like their videos, which while some backers think they are there to show how wonderfully open CIG are, i'm more cynical and think they are there to get people to spend more and rope in new backers.
Then of course, there are their "gifts" to faithful backers. Top of the line PCs they gave away to prominent streamers. Who paid for those?
We also get an idea from CIG's financials they burn through around 50 million per year at the moment (with current staffing)... maybe higher (someone want to correct me on this?).
Therefore the clear answer is Xink knows how to deliver SC for a fraction of what it takes CR!