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

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.