Prices and window were clearly set on purpose, starting from the number of minidiscs. The size of the originally-leaked material was actually different, so the final one might be coincidental or they might have “targeted” it with strategic padding to be cute.
You don’t have to be a cynic, this is Radiohead - they literally gave away what could have been their biggest-ever album, and don’t really need any publicity to sell out venues.
The only real coincidence here is the MP3 size equaling the number of discs, but I think it’s possible to target a total size with MP3 encoders so that could even be set on purpose.
The total MP3 is 1.8gbs. The selling price is £18. It’s on sale for 18 days.
To me it seems clear that they just took the 18 number, decided to own it, and went from there on in everything else.