Valuations and fundraising

I was talking to a buddy of mine that's been through a few rounds at a few startups. One interesting point he raised is that investors want to own 25-30% of a company after they've invested. In his opinion, this was a hard lower limit.

What this means is that raising $250k implies a $1M valuation.

And that if you really do think you're worth $4m, you should raise $2m for a post-money $6m.

Have others found this to be the case?