6% investment, diluted three (two rounds after seed according to http://www.crunchbase.com/company/dropbox , plus the current one), that goes down to about 2% (diluted by 30% each time).
2% of $4b is $80m. That's a 4000x return over what, 4 years?
pg has been on record saying that financially, YC does better if the YC companies go public, not if they sell out early for $XM or $X0M. But he supports those because it benefits the founders, and when founders win, YC wins.
Back of the envelope maths:
6% investment, diluted three (two rounds after seed according to http://www.crunchbase.com/company/dropbox , plus the current one), that goes down to about 2% (diluted by 30% each time).
2% of $4b is $80m. That's a 4000x return over what, 4 years?