If Companion cube isn't, What is the *actual* most expensive thing in Terraria?

In Terraria, you collect money to buy stuffs. You use those stuff to.. well, get more money, I bet. But what do you do with all that money that you just got? It's one of the hardest question, maybe you just make a vault and dive into endless amount of coin, just like that duck. Or, just spend it into some weird creature that loves to follow you. Pet items are one of the most expensive items in game, and Companion cube, costs 5 platinum. It is the most expensive thing in game... normally.

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Chapter
0:00 Expensive Expenditure
1:50 Traveling Merchant and the Companion Cube
2:55 The second most expensive thing..?
4:36 And 5.625 plats is equivalent of 5,275,000 coppers.
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[Outro/Custom song]
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Most of the musics used on this video was either taken from video game, or copyright-free musics from Youtube Audio Library. The name of the musics will be mentioned down below.
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Used Music:
-Terraria Town day
-English Country Garden
-Terraria calamity: wasteland
-[outro]
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I hope you have a great day, as always!
Thanks for watching, I guess.

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