Ron Jeffries answered in the XP list to Jim Hughes.

 > Ed has tried what you suggest.  When the bosses want 10 things and our
 > > measured velocity indicates we're going to get 6 done by the date, the
 > > bosses reply with "how many contractors do you need to get it all done?"  Ed
 > > says "We could use a couple more good coders; maybe we could get 7 done if
 > > we get them in soon.  Any more than that will slow us down, because helping
 > > the get up to speed will take up too much of our time."

 > > "Okay, so how many contractors do you need to get to 10?"

 > > This exchange really takes place over weeks, not seconds, and involves many
 > > more people.

 > > I realize that what Ed's bosses don't "get" isn't just Agile, but basic
 > > proto-agile wisdom about how software development works, like in The
 > > Mythical Man-Month.  Ed is looking for a way to help them get it.

 I'd really need to hear the real conversations to know what's up.
 But the answer to the first contractor question probably ought to
 be:

    Adding one contractor will slow us down for 45 to 60 days, then it
    will add X percent to our speed.

 The answer to the second is probably something like:

    There is no such number. We can't vacuum your office in ten
    seconds by using a thousand cleaners. They won't fit in the room.