There are two areas where increased die size affects number of dies per wafer:
The impact of defects is difficult to know unless the manufacturer releases the details as redundancy or disabling defective areas affects what you can use. On top of this, the ability of the design you are using to be successfully etched will then give you your final yield.
From what I can tell, on the AMD side, the Zen2 CCX should yield between 750+ dies per wafer based on its size - I've ignored the IO die as it shouldn't affect the number of usable parts significantly. Yields are reportedly in the 68%-73% range.
On the Intel side, the 4-core Coffee Lake is around 415/wafer and the 8 core part is around 275/wafer. Yields are reportedly around 75%-80%. Intel benefit from a more mature process with yields.
I've assumed 300mm wafers for all parts.