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So that's the main test here; in order for the band to come out ahead, Radiohead needs to clear only more than a buck-50 per sale. Easy.
They only need to clear more than 1.50 per sale if they sell the same amount. That's the gamble, that they can sell enough without the label machinery, and possibly with the active opposition of the entire industry.
I have no idea what the prospects are, but >$1.50 per sale, on its own, isn't the break-even point.