I checked.

They are renting about 35K DEC worth of cards.

Trouble is they can do this because there are still lot of "lazy renters". Aggy is one. He hasn't changed his prices in ages until last week. He was giving away CL max summoners for 10DEC :)

There are more like that. Cheap rental are not universal. They also require automation. Publicly available rent bots disappeared. So many common people can't use them to snipe cheap rentals.