A group of publishers and tech companies gathered in Washington today to talk about getting digital textbooks into U.S. classrooms. The gathering, convened by the FCC and the Department of Education, included everyone from Apple to Intel to McGraw-Hill, and it was premised on the idea thatdigitizing classrooms is a good thing.

And, for argument’s sake, let’s say it is. But not because doing so will save schools much money. At least not anytime soon.

Here’s a report from the FCC that compares costs, per student, for a traditional classroom and one that uses tablets. You can see all of the assumptions on the first page of the document, most of which come from an education/tech consortium, but the important things to note are:

• The model assumes that the tablets the students use cost $250 apiece today, and will drop in price to $150 in the “future.” Presumably this assumes that device makers end up working some kind of bulk purchase price with school districts.
• But even as hardware costs drop, other costs won’t. Which means that while a school that equips its kids with a tablet and a mobile data plan will theoretically save $34 a student per year today, those savings creep up to only $60 a student in the “future,” even though tablet costs will have dropped by $100.

There are more than 49 million students in public elementary and secondary schools in the U.S., so $60 a student per year is still real money — nearly $3 billion. But based on the math in these charts, that’s still less than 2 percent of the outlay per student per year. Which means there had better be lots of other reasons to make the switch.