Amazon has a special sale on the 512GB Samsung Micro SD card. Regularly $199, you can get it for $129, at the time of this writing. For a lower cost per GB, get the 128GB for $20.99 (that’s the lowest cost per GB), or 256GB for $49.99. All of the cards support U3 speed.
Please note that many 360 cameras have limits on the maximum size Micro SD card that they can use. TBH I’m not sure if any of my cameras will be able to use 512GB, although one user has reported being able to use 400GB on the Insta360 One X. I will post test results as soon as I’m able.