Approximately 100% salary overhead is pretty standard, so eight $125k employees plus infrastructure and office costs sounds reasonable.
Anyway: considering what they do and where they do it, I don't find these numbers high at all. I would be shocked if they didn't have at least a couple engineers making over $200K in actual cash compensation if they're working in the Bay Area.
Overhead doesn't scale linearly with pay. Once you're into 6 figures, it's definitely not equal. I'm guessing much more like $150-200k per employee in compensation.
The standard overhead is (I believe--correct me if I'm wrong!) anywhere from 25% to 100%, depending on your base salary and how competitive the benefits package is.
Edit: Missed the first part of that, I apologise. 100% overhead doesn't seem reasonable per employee to me though.