Juicero is the commonly mentioned one.
<a href="https://en.wikipedia.org/wiki/Juicero" rel="nofollow">https://en.wikipedia.org/wiki/Juicero</a>
Maybe not the most expensive, but one of the silliest - AllAdvantage <a href="https://money.cnn.com/magazines/fortune/fortune_archive/2000/07/10/283752/" rel="nofollow">https://money.cnn.com/magazines/fortune/fortune_archive/2000...</a>
Here's a recent site listing 200+ startup failures with approximate funding amounts.<p><a href="https://www.cbinsights.com/research/biggest-startup-failures/" rel="nofollow">https://www.cbinsights.com/research/biggest-startup-failures...</a>
Star Citizen is a video game that had a crowd-funding campaign in 2012, ten years ago, and has since raised over $500 million from its player base and another ~$150 million from private groups.<p>It's still in alpha.<p>Most of the player base have resigned to calling the game vaporware.<p><a href="https://en.wikipedia.org/wiki/Star_Citizen#Delays_and_extended_development" rel="nofollow">https://en.wikipedia.org/wiki/Star_Citizen#Delays_and_extend...</a>
In a sense, Uber. Billions of dollars invested with the promise of winning the race to self-driving. It wasn't the only massive mistake they made, but after they killed that homeless lady in Arizona, they killed their self-driving units as well.
Probably not the most expensive but certainly one of the most prominently featured failure in the early days of the internet.<p>Govworks.com by that sleezy dude Kaleil Isaza Tuzman.<p><a href="https://www.youtube.com/watch?v=Pjk-WmtNs3g&t=19s" rel="nofollow">https://www.youtube.com/watch?v=Pjk-WmtNs3g&t=19s</a>