I am no expert, so take this with a grain of salt. I have done a little bit of reading on starters and it seems like people try and keep them in the 1.030-1.040 range. I think Jamill even suggested that he keeps the gravity in the starter at the lower end so the yeast get going, but they are hungry when you pitch them. There is some good info here:
Fourteen Essential Questions About Yeast Starters
One thing I found particularly interesting is that he suggests the same gravity in a starter for a big beer because a high gravity starter will stress the yeast.
Primary 1) Empty
Secondary 1a-f) - 2 gallons Traditional Mead, 4 Gallons Melomel, 2) Wee Heavy Widgeon Ale, 3) Pintail Pale Ale
Bottled - Amber Ale, TheJadedDog's All Amarillo IPA x2, Apfelwine, Wit Bier, Stout, Pintail Pale Ale (V1-Cascade, V2-Amarillo), Graff