Apple's recently introduced $899 iMac will be available to a narrower audience than originally estimated. The low-cost machine was intended to be used in educational institutions, by teachers and students, but never beyond that. Students aren't going to be able to purchase one on their own, and nor will anyone else. The page for the machine has been updated to reflect this:

According to Apple, the $899 iMac will now only be sold to education institutions only. Apple originally indicated that the iMac would be immediately available to education customers, which is usually what the company says for other education-only Macs discounts and products.
Some speculate that Apple believed they would be undercutting themselves if they made the lower cost iMac widely available, hurting sales of the pricier machines. That may make some sense, though it would have been advantageous for students to be able to get a lower cost machine, especially when cost is often one of the biggest driving factors in a student's purchases.