Slack and Github were so worried about someone cybersquatting that they were willing to pay $11,500 each to get those domains today? I guess that's the point of the Dutch auction system, but still seems like a waste of money.
For Microsoft (which owns GitHub) that is a tiny expense, but if they couldn't really afford it they could just file a dispute under UDRP.
In a lot of the large companies I've worked, money is siloed from one operating unit to the next. They would send bills between units and sometimes even departments.
The larger the company, the more common this seemed. It's not one giant piggy bank.