Super-rich guy building space ships plans to ride on other super-rich pal's rocketships too

Apparently, Elon Musk is going to ride on Richard Branson's rocket.

Space:

Branson told The Sunday Times that Musk has put down a $10,000 deposit to reserve a seat on a future suborbital flight, and a Virgin Galactic spokesperson confirmed the news to The Wall Street Journal. (The most recently stated full ticket price is $250,000.) It's unclear when Musk's flight will lift off.

Whats $250k between buddies?