Comment by nikcub

That is a problem with the YC model in that they can't (or don't) fill follow-on rounds and are thus diluted.

Most VCs that invest in an A will set aside 3-4x that to invest in later rounds (Fred Wilson wrote a post about this recently)

(ps. your pre values are way too low (the 3 at A was probably on 10) but the point of dilution still applies. They also would have sliced out a 20-30% option pool at A)