Why is whey protein so cheap compared to casein

Whey protein is usually the cheapest form of protein powder I’ve seen. Cheaper than other milk based proteins, plant based proteins, etc

However my understanding is that cows milk produces protein that is 80% casein, 20% whey. And I’ve noticed casein protein is far more expensive. Usually twice the price of whey

So if there is 4x more casein protein, why is whey the cheapest? Is casein used for something else and whey is just a useless byproduct?

Whey is a cheese byproduct that they need to find a way to dispose of otherwise. It’s also been a big issue in the yogurt production industry with tastes shifting from thinner stirred yogurts to thicker Greek style yogurts. It has become a major environmental issue: https://modernfarmer.com/2013/05/whey-too-much-greek-yogurts-dark-side/

Because whey is a byproduct of cheese making, while the casein stays in the cheese. So whey protein is basically industrial waste that’s being repurposed as protein supplements.

Well that was easy to answer. Thanks.