artificial diamond isnt so expensive, and i imagine you wouldnt mill a block of diamond into a heatsink - more likely it would be of an old slab design like the stock thunderbird or northwood heatsinks, with fins growing out of the top. lay down several sheets of diamond layer up to a certain thickness (tbd by the thermal load and die size) then grow the diamond up in stripes - resulting in fins.

I agree, diamond would provide much better thermal conductivity, but it would also be very expensive to manufacture into heatsinks as its such hard material. It wouldn't be worth the cost as people wouldn't buy it.

...and what about lapping. It would take ages to do using regular 1000/1500/2000 grit sand paper.

Ive lapped a thermalright copper heatsink before quite easily.

Copper as raw material costs about 50 euros a kilogram, so I guess the price is not that insane after all.

Pure crystalline diamond has about 5 times the thermal conductivity of copper at just under 40% of the density. This should allow dramatically lighter heat sinks (along with dramatically lighter wallets).

I'm really not surprised that Western Digital's new 1GB 3.5" Hard Disk Drive is quiet and power-efficient. It's not exactly frontier technology their pushing, it would seem.