Science Publisher Elsevier's reported profit margin is 38%, compared to Apple's 21% – there's lot of cash at stake for them and a big warchest to defend it
For anyone looking to understand the background on the science publishing industry, how it ended up this way and why they will fight Sci-Hub so aggressively, I found this discussion really informative: https://www.youtube.com/watch?v=PriwCi6SzLo&t=8s&ab_channel=...