This is confusing the two meanings of free that FSF tries so hard to fight. RMS doesn't care about paying for documentation (the FSF supported itself for quite some time selling docs and tapes). They care about free sharability of software, and by extension information about software. And yes, from that perspective the non-redistributable stuff from O'Reilly isn't something the FSF is interested in supporting per se.
I tried not to confuse them, but don't seem to have done a good job.
You are correct, the non-redistributability of many O'Reilly books is what they would they would object to, not cost. And not all O'Reilly books are non-redistributable - they have a number of books under open licenses.
