Depending on if, or how often, you die. The right group in the high twenties, low thirties doing drow warrior students will also get 800-1200 each, but getting past the patroller is always a chancy bet (which I'ven ever understood because the patroller is worth less exp than the students). For the imms, I'm sure it's a matter of balancing the risk reward ratio - there aren't that many places in the 20-40 range that are dangerous enough to have mobs that give that much experience.