Unable to complete album purchase on iTunes: 'You've already used one of the items to complete another set' error

How to download an album when it says "Unable to Complete Set: You’ve already used one of the items to complete another set."?

Apple has made it impossible to purchase the album at all in this case. Deleting the song does not help, there is no option to purchase at full price either.

I cannot fathom a reason for such an asinine decision to only allow a purchased song (single) to be used to complete one album, with no ability to switch which album said single completes. Or why there is no option to purchase the album in full.

The only apparent solution to this problem, which only a few others have posted about, to no response, is on Apple's end.

[Re-Titled by Moderator]

Original Title: iTunes Complete Album