I grew up in casette and CD era, so I use that for comparison. It’s a bit of a stretch, but it works for me:

An album or cassette had roughly 10-20 songs and cost (in today’s inflation) roughly £5. Not all songs were bangers so I round it all to £0.5 per song.

How many listens to be “worth it” I think is how much listen I would get out of it before I would happily buy a new one if it wore out or broke. So at least 50.

At price of £0.99, I think a song is worth it at 100 listens.

Though songs bought to support indie artists are worth it immediately. :)