The number of chips per wafer varies considerably, depending on a range of factors which obviously include the size of the chip and the diameter of the wafers, but can also be significantly impacted by the defect rate. It can range from hundreds of chips at the low end to tens of thousands at the high end.
For a System On a Chip (SoC) like the A14X expected to power the first Apple Silicon Macs, it’s likely to be in the hundreds. This would suggest initial capacity in the single-digit millions per month.
A report last week suggested that one of the first ARM-powered Macs will be a revamped version of the 12-inch MacBook.