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I believe that holiday tonics will follow the pattern of what happened for the Endless Halloween Tonic. Endless Toy Maker's Tonic is around 30 gold buy out currently, but the one from Halloween is up to 230 gold buy out! If I'm right, then the Endless Toy Maker's Tonic will go up within a few months as well.
Might be worth picking up now while there are a few dozen on the trading post.
If you've got the gold to burn, buy one or two and let those collect dust for 3+ months.
Same with other holiday items that should rise just as the Halloween ones did.