When doing calculations, it is better to use the average of 75 days. So 70K paid for six employees for 75 days (given in the article), which is about a fifth of a year. So 70*5/6 = 58K per employee per year.
75 * 6 devs = 450 dev-days, or 1.23 dev-years. 70K/1.23 = 56.9K. According to Google, that's $51K USD per year.
Yeah, I can't imagine why rockstars aren't beating a path to his door.