that is already disproven, because eligius pays already more than many pools for example deepbit. deepbit has 4661 Gh/s and eligius only 450Gh/s, but eligius pays 10/9 per share in comparision to deepbit. if it's all about the money they should have switched a very long time ago...
The individual utility function of miners does include more than just price/reward per share. Eligius is small and only has one server, is still experimental, has a history of being offline for hours at a time... people might find it's "worth" earning 10% less if they on the other hand have a more stable connection. Then again, bigger pools are more likely to be hacked / attacked / DDoSed / botnetted... It's not all in the price.