> talk is cheap and ideas are cheap, but people are really expensive [...] because the idea will change over time anyway.

I largely agree with this sentiment in general. However, all ideas are not created equal. Most successful companies seem to make 2nd order corrections and refinements to their ideas, but not change them all that much. Case in point, facebook hasn't changed that much in terms of vision and what it provides for its users since it started. Same for google, apple, airbnb, heroku, dropbox, reddit, mint, basecamp, ...

[i don't mean to say that those are the same type of success, just illustrating that what i said applies to a lot of very different types of successes]