By now people have figured out you can actually sell the Hearthstone toy – and it is selling (screenshot is from the WoW Econ Discord).
The achievement you get from the event is account wide, so you can’t obtain that again – but to get multiple toys, just log in to your WoW accounts (if you have more than one) BEFORE you complete the achievement, and every character that is online will receive it.
** IMPORTANT** This COULD be changed in the future, it’s probably meant to be BoP – so be aware of that fact.
Save them until after the event and they become more rare, or sell them off before any changes happen, that’s up to you.
Happy gold making!