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.
But does the money come from Microsoft or from GitHub?
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.
If you buy the domain during trademark holder's period, you pay the normal price, and not the day 1 landrush price. So no, Slack et. al. did not pay $11,500 to secure their name.
But note I think you mean the $12 price but that’s only available from the 28th Feb. To buy today it is $11,500 (unless as others have pointed out you got it as part of the trademark sunrise period)