$0.50/L here. Don't take the first price if you're a bargainer. I went from $6/L at Airgas to $1.75 after talking them down. Then I went to a local welding shop and talked them down to $1/L. After using a friend's receipt (from a different region) at my Airgas I convinced them to honor $0.50/L. Same Airgas, same people. It's all in how nice and how persistent you are, with a little luck thrown in for good measure.
EDIT - Forgot to mention that's with my own 30L dewar. I can rent a 180L for something ridiculous like $1.75/day plus $5 delivery charge. Those are rough figures but you get the point...I like my local Airgas.