I don't think I'd go that high.  For the last couple months, you could get lots of good, younger breed ewes for $310 and you got lambs out of them right away.  He's looking at 10 months til he sees a lamb, and probably 15 months til payday.  I would think $200-225 for the good girls, and the short timers probably $125.  Culls are bringing around $75 a head now. 

Anything with a bad bag you don't want, so check them, and make certain he dried those ewes up properly before the lambs were weaned, or you will have all kinds of bad bags next year.