A one carat diamond may be worth $10,000, but if there were suddenly a trillion of them, they would be worth next to nothing, and people would use them as gravel in their driveways.
It's funny you should mention that. Suppose that if there was a trillion of them, and suppose they were controlled by one monopoly who could regulate the supply say by hording cut diamonds and trickling them out into the economy. You'd actually be in a very similar position to where we are today.
Diamonds are not rare, we can manufacture them quite easily without imperfection. A 1ct diamond can be made for under $2500 The value comes from the fact that people want the single biggest one, all natural dug out of the ground, and perfect in every way. Where do you find diamonds like that? Horded in De Beers safes, and when they announced a transition to end that 80 year long practice of price manipulation it was accompanied by a marketing campaign that just made your recognise that crappy little 1ct diamond for the crappy little 1ct diamond it is, not worthy of your fiance's love.
Diamond as a material is quite abundant and costs $40/ct. I have a toolbox full of products that contain collectively over 1ct of diamond, but industrial uses aren't manipulated by marketing or supply side market distortion.
Now if I had an asteroid in my back yard worth $10 quadrillion, do you think I'll just sell it on the open market at once?