[larrys]

"I don't think yCombinator failed to see the market potential, in my view they are actively looking for potential "

Much of life as we know does have a luck factor involved.

Who is to say if they had spent the money (could afford to) to fly all three people out and not been near the last interview whether the outcome would be different?

Maybe. Maybe not.

Thing is you never know about the minor details that lead to, or prevent success.

When I was younger I once spent my own money to fly out to a trade show, stay at a hotel, walk the floor and as a result landed a job that I wasn't really qualified for that I would have never gotten by resume alone (that I am pretty sure of). [1] Perhaps the person was in a particularly good mood that day perhaps I just said and did the right things. I could spin this story a dozen ways (depending on the point I was trying to make).

My general rule though has always been to "spend money to ensure success". The downside of spending money is very clear (it's finite, the amount of money that you spend and of course the time in this case. Ok sure there is opportunity cost as well.). The upside is unlimited. As a generality people tend to focus on the upside and not the downside in decisions.

[1] There was also quite a bit of leg work upfront prior to doing this as well.