20% of a very large number is still a large number. There are lots of very profitable businesses that have a ~1% profit margin.

That doesn't mean 20% is their profit. It means all the rest of their overhead has fit into that 20%, such as hosting infrastructure, office space, labor, marketing, etc.

Oh no, how will they cover overhead with 20% of tens of billions of dollars!?

Costco is famously about 2% or so, which is basically the entirety of their membership fee revenue, iirc.

80% of a very large number is an even larger number.

It’s not like they have any control over this. What should they do ? Yeah they could say fuck-off to Universal & Co but it would be their instant death.

Right holders made them sign extremely strict contracts which disallow Spotify to diversify themselves. Notoriously, their contracts with majors states that they are forbidden to develop their own in-house label.