One would guess that the coming pay-what-you-want Radiohead album is not distributed in the pay-what-you-want version by a record label but by the band itself. This alone could make it worthwhile for the band. As Courtney Love wrote a few years ago*, the labels are greedy, to the point of skilfully navigating deals so that income does not come from licensed music (for which they pay royalty to artists) even if the thing they are selling is still access to music**.
If Radiohead gets 100% of the income instead of 20%, then a few dollars for the entire album on average works out very well for them compared to the usual distribution channel.
As an aside to that: I have no idea why Apple has not done what Amazon did for booksales, opening the shop up to anyone who can deliver the music to the store, but are leaving that to third parties.

* Note however Love's slightly phony math: She does not include the royalties earned by the band in the equation, nor the very real risk on the labels investment (i.e. all the money they lose on non sellers in their catalog)

** As far as I understand the RIAA does not actually pay out any money from settlements in their thousands of lawsuits to artists, as an example.