I was researching this today. Most expensive cubes in the world:

1. The Kaaba in Mecca: Literally transcends monetary value

2. Apollo lunar samples as cubes: $1M+/g

3. CubeSat: $100k-$1M+ each

4. Osmium cube: $50-80k/kg

5. Ancient dice: $100k+

6. NYC Apple store: $6M+

Thanks for your time.