In return you have a fixed cost of a $600 device with a finite shelf life (which could easily buy at least 1 year of K-12 textbooks for the student). The lithium batteries on the iPad will not hold a charge forever and neither would Apple support any iPad version for more than 3-4 years (see iPad 1).
It's possible to keep an iPad for 10 years. If the graduating students don't get to keep the iPads, and anyone who breaks it has to pay for it, they're saving (according to you) $60 per student per year with a $600 iPad cost every 10 years. It would balance out. However, I have heard from other people that the savings on digital textbooks are much higher.
Realistically, this won't happen. It's not their money, but it makes them look good when they spend it; they'll keep buying new iPads, iMacs, and those retarded Smartboards.