Comment by grues-dinner

Depends on the chip. A typical consumer processor is 100-200 mm². Wafers are about 1mm thick (actually a bit less, but close enough) and silicon has a density of 2300kg/m³. So it's 2.3mg/mm² of wafer area. The chip is then 0.23-0.46g. if it's high end and worth $1000, then the wafers are $2-4000 per gram. Probably the low end of that since the fancier chips are usually the physically bigger ones.

However, low-end processors will be worth radically less ($100 CPUs aren't 10x smaller) and things like top-end FPGAs will be worth substantially more. An Agilex 7 can be $40,000 and if it's got less then 4 grams (around 1700mm², or 41mm*41mm), the wafer is worth over $10k/gram. The entire chip is 56x56, and from the package drawing, the die appears to be around 30x30, so it exceeds the threshold.

This is assuming all the value of the retail price is the main wafer, which is also not true.

Thousands per gram, certainly seems possible, though I doubt it's even that on average across all chips, and considering that there is non-wafer content in the price. Tens of thousands is probably pushing it. However, it's certainly likely to be rather more than gold in terms of specific value ($100/g, ish). Harder to fence, though.