Don't quote a number, quote a multiple instead. :-) eg. If XX invests 20k for 10% in your company. their 20k becoming 200k is a good deal which implies something like 2M for your company (not bad for three months work!)
A follow up thought. This also puts XX (may be YC in this case) in valueing your company just right! (Ok YC are nice people so thats not a problem, but if you were asked this question in other context, you better be prepeared!) 'cos they cannot value your company too low. 'cos even if someone is willing to give 10x of their investment, you may say "No Deal" and if they value your company too high (like some VCs do), it almost rules out probability of a nifty 2M$ acquisition. (This is again from Paul's essays)). It's almost like RTFM :-)
