In my opinion, we need to stay away from this kind of comparison, there is certainly a huge difference between Bitcoin , Diamond, Gold, Silver and even FIAT and of course all of them are valuable for us.
In fact, remember that Diamonds are really expensive and not available to everyone, so it is not that easy to make a demand supply curve also the market of diamonds is really different comparing to crypto.
Well the very reason why these things are being compared is because of the value and volatility it contains not necessarily the exact thing or how they appear on everybody. I want to exclude the fiat from the things you have given since we can just print it out in a thin air. Precious metal and stones such as diamonds, gold and silver is tangible and the costs of it depends on their physical properties that is why diamond is more expensive than gold and gold is more expensive than silver. However, bitcoin is included because it also stores a value like the said metal and stones. What only differs the bitcoin to the other is the volatility it contain which is higher than the diamonds, gold and silver.
In fact, remember that Diamonds are really expensive and not available to everyone
Diamonds are expensive but the amount is always is always the monetary equivalent that is why it has a least amount called carat, where in bitcoin it is called satoshi.