In one project we had testing setup which costs 600k USD allually. It was three times more expensive than production setup we had for product which was more than 3 year old. Nothing special, just mongo and Kafka with enormous size. If you run automation tests Manu times per day but do not clean anything - you'll get mongo with terabytes of test data. And then, on top there was elastic search which multiply bills.

Dev env. for complicated products can be fairly involved and large companies might have a lot of them.

If you're dev doesn't look like production, then you're not testing in reality.

have you met SAP? :)