During the Destiny 2 press release event, it was revealed that the PC version of the multiplayer online FPS will be available exclusively via the Blizzard App. It is an unprecedented move, as games under the Activision brand of Activision Blizzard have always been launched on other launchers on PC. The use of the Blizzard App will let players of Destiny 2 use all the features of that launcher, from friend lists to Facebook Live streaming.
It will be possible to use Blizzard Balance, real-life money that can be added with a card and also gained from other in-game currencies, like World Of Warcraft (WoW) Tokens.
WoW Tokens are special currency that can be used to extend your WoW subscription or sell for gold (in-game currency). It can also be exchanged for Blizzard Balance to buy games or other premium items. As detailed in the FAQ here, Blizzard Balance can be used to buy Destiny 2, and players have started investing on WoW Tokens due to this.
These Tokens are available for purchase with both gold or real money. As such, the price in gold can fluctuate due to high demand. The European realm reached up to 251,000 gold per token, with North America spiking up to 140,000.
The price has gone down again, but it serves to show that there is interest of Destiny 2, especially from players who are already invested in the Blizzard ecosystem (and more particularly, players who are already playing an MMO).
Destiny 2 is set to launch on PS4 and Xbox One on September 8, with the PC release coming sometime afterwards.