What would the cost be of visiting an asteroid? I'm trying to think through what the cost would be of an unmanned mission to a nearby asteroid.  To me it seems like the high-level costs would be the fixed cost of the "spaceship" itself (including any scientific or mining equipment required to carry out the mission), the cost of getting into orbit which would depend on the ship mass, and the fuel to get there and return (which would be a function of fuel cost, ship mass, how fast you want to get there, and the mass of anything collected at the asteroid site that would be returned).  Is there anywhere that this is discussed or has anyone thought this through further?
This is something that has already been done, so we already have a point of reference. Hayabusa landed on the asteroid 25143 Itokawa in 2005. The mission was considered a success and a sample was returned to Earth. According to sources from the time, the total mission cost was around 170 million dollars and other sources put the development cost of the spacecraft at around 138 million dollars. There is also a planned Hayabusa 2.