They've been doing this for as long as I've been on pc, which is 12 years. Actually, before refunds they had flash sales which were even lower. They rake in billions per year as a private company. I'm sure they'll be fine.

The games that get reduced that heavily generally are years post release. Without those sales, they probably wouldnt sell at all anymore. I doubt that this is negative business for valve

Because games that are that heavily discounted are past their sales expeditions and the orgs don't worry if the game sells more or not.

Maybe because those games don't sell without a discount.