We always use Sheba Limo (714) 632-5172 for airport travel. We live further out from LAX than DLR, and I think we pay around $100, though it has been a while so my memory is not so great. I do remember, though, that it was less than Super Shuttle, which I believe charges by the person, so for the 4 of us, it was really high. There is one shuttle service out there that is supposed to be the best (lowest cost and no rides with strangers) I think it is Prime Time Shuttle and I think it is about $80. They have an option to share with strangers for less cost, but I never think it is worth it because of the extra stops. However, since you are going to DLR, you have a good chance of riding with someone going to the same place.
This is the second post I've made on Sheba today. I think they should put me on the payroll.