Trader’s Tender is a new currency used to buy goods in the Trading Post. As a “Thank you” to the community, Blizzard is awarding a bonus 500 Trader’s Tender to players who purchase(d) Dragonflight.

(Source)

It won’t be long before the new Trading Post* feature goes live, and with its arrival, players with Dragonflight will receive Bonus Trader’s Tender.

What a Tender Moment! 

As a way of saying “Thank you” to the community for continuing to play World of Warcraft with us, we will be awarding a bonus 500 Trader’s Tender to players who purchase Dragonflight and add it to their account**. This bonus Trader’s Tender will also be rewarded retroactively to players who have already purchased Dragonflight. Players can collect this bonus Trader’s Tender once the Trading Post feature goes live from their Collector’s Cache.

*Requires World of Warcraft Subscription or Game Time. The Trading Post feature is not available in WoW Classic titles.
**
Bonus Trader’s Tender is granted only once per Battle.net account.