So how much DOES open access publishing cost?

Considering that the pricing of standard model serials subscriptions is often shrouded in secrecy and non-disclosure agreements, I thought it would be interesting to further investigate some of the costs of open access publishing. To that end, I dug up some links:

• PLOS Publication Fees (It's interesting to note that prices here haven't been raised since 2009)
• Springer Open Access Fees
• Elsevier Open Access Articles
• Oxford Journals Open Pricing

Obviously, there's quite a range of pricing options depending on the publication and the company that owns the publication. On the surface this method of payment for publishing seems cheaper than the current model, but it raises its own questions as well. For example, how would an additional cost like this on the researcher's end affect research and publication? And how would it affect library budgets?