For manned space flight, so far 18 people have died out of 430 that went to space. (14 Americans in two shuttle accidents, and 4 Russians in two separate incidents)

That's only slightly lower than 1/18.

The shuttle had a 40% vehicular failure rate (2 out of 5) and a 1.5% flight failure rate. That's better than 1/18, but not by that much.

Clearly, manned vehicles demand a higher level of reliability than cargo carriers. However spaceflight even after decades of experience is still pretty risky. From a life safety perspective, non-manned, robotic missions are preferable. But our drive as a species to explore and populate new territories means that we'll need vehicles safe enough to travel in, and/or people who want to do it regardless of the risk. 1/18 is still probably decent odds compared to the ones facing people 300 years ago, who set out in wooden sailing ships to explore the unknown.

With manned spacecraft, you have to factor in the chance that the crew would survive a failed launch. Specifically, in the press conference following this latest failure, it was stated that the planned crew escape system would have been capable of saving the crew. To my non-expert eyes looking at the event, there seemed to be a fair amount of time between there being an obvious problem, and complete disintigration.

At some point, yes, there is a monetary value to human life. During the early days of space flight, it was something like $1 million per astronaut. These days, it's up to something more like $50 million per astronaut (inflation would put it as more like $7 million).

I don't have my original source on this, but here's a good article discussing that and the concept of "mission success": http://reason.com/archives/2012/01/26/how-much-is-an-astrona...