CLEAN : Raj Pink diamond to be sold by Sotheby's

The video discusses an upcoming auction in Geneva featuring a rare pink diamond. This diamond, graded by the Gemmological Institute of America, is the largest fancy intense pink diamond ever recorded, weighing 37.3 carats. Its rarity is emphasized, as only a small fraction of diamonds have a pink tint. The estimated value is between $20 and $30 million, but its unique nature makes it difficult to predict the final price, which will depend on buyer interest.

Why is the pink diamond considered extremely rare?

What challenges are mentioned regarding the estimation of the diamond's value?