The Cornell Library based arXiv.org asked for assistance with their open access pre-print server. The cost to run this operation is equivalent to an entire physics library's purchasing budget, or $400,000. Cornell Library hopes that these funds will help sustain operations and continue development of the arXiv.
Based on the ranking of institutions representing the most active users of arXiv each institution will pay a tied sponsorship starting at $4000 (UMN ranked 64th in use in 2009).
Read more about Cornell's new model in the Chronicle's 1-25-10 article "Cornell Library Proposes New Model to Keep arXiv Going"
Also, read the "arXiv Business Model White Paper" which is, or course, posted in the arXiv.