Here is an interesting interview with Kari Paulson, President of eBook Library. They either (1) sell books to libraries at list price and allow a fixed number of people to consult the book each year (2) sell short-term access to the book for 10% of the list price.
The business models are sensible.I guess Google eBooks will put them out of business in due course, quite possibly using similar pricing arrangements. I think this is the future of technical libraries but am not sure about general libraries.