- 3 months of intense focus on product and growth with feedback
- access to and advice from YC partners
- community of other founders in the batch who are going through similar issues
- access to other YC founders (partnerships, advice, etc.)
- social proof to investors, press, customers of having done YC
In that case, YC is tremendously helpful in giving the platform to raise enough money to do all of the hard things involved in building a plane that's never been built.
Time is the most precious resource in startups. One way to get more time is to have a phenomenal team, so you do things faster (either by building the right things faster, having the expertise to not build the wrong things, etc.)
Another way is by having more money, so you have a longer time to figure things out. When I say that the $120k isn't what is valuable about YC, I don't mean money in general. The fiscal benefit just tends to come indirectly, from access to platforms (Demo Day, press), investors, and pitch advice.