Thanks. I estimated the value based on spectral class, which gives us an idea of composition based on how they reflect light. I combined this with current prices for materials mostly from the London Metal Exchange. Other costs such as getting to the asteroid and mining overhead are factored in.

This sounds awesome, nicely done.

I've been planning to do a hack like this to demonstrate the realities of interstellar travel, modelled after a game I played as a child.

Have you shown this to Planetary Resources? Just for the fun and some PR of it (at least)?