Fair point. Total cost may be lower with this approach than the current situation where textbook manufacturers leverage their position and IMO significantly overcharge their often captive audience. So assuming the ipads can be kept in working order as long as paper books its cheaper.
But its not as cheap as it could be if the format was open so other device manufacturerers could compete to build the best low cost hardware for schools. As it stands its mainly just moving the lions share of the income from textbook publishers to apple.
The right thing to do IMO is to focus on a standard open format so there can be increased competition not just on the cost of the books but on the hardware as well. Schools need sustainable barganing power to get the best materials for their students now and in the future. Vendor lock in takes that leverage away.
Such open textbook innovation is already happening without apple. I applaud Apple's effort to innovate on the format to provide richer more teacher customizable content but I can't get behind the lock in even if its somewhat cheaper up front.