3D V-Cache in the only SKUs on the market right now (5800X3D and Milan-X) is 7nm, just like the CCD beneath it. IOD is Glofo 12nm on that.

On GPUs this strategy isn't working out too well for them right now. Their 7900 is a lot more silicon with a lot more transistors (300 mm² of N5, 220 mm² of N6, 58bn xtors) compared to the competition (380 mm² of N4, 46bn) [1] and is marginally faster in some cases, drastically slower in others, and uses much more power in every case.

[1] While AMD uses two slightly older processes, AIUI the overall packaging and silicon costs are speculated to be quite a bit higher for AMD compared to nVidia here.

I don't think comparing chiplet sizes by summing the area is a good way of doing it, because smaller nodes cost more and have lower yield, and smaller individual chiplets mean way less loss per-wafer, as the bigger the size of a single usable unit, the more chance something is broken and it isn't usable. Losing one or two small chiplets is a lot cheaper than losing entire chips in a monolithic setup.

AMD claim that producing a 16-core Ryzen CPU without chiplets would have cost them twice as much. You say that the GPU strategy isn't working out, but I think that really depends on what their pricing strategy is. I suspect they just don't feel they can take the market right now, and are making a lot of margin while the market will support it, rather than trying to compete on price at this moment, but I admittedly don't have any evidence for that.

I guess we'll see, but it sure seems like there is a lot of advantage to building the way they have to me, I'd personally be surprised if it didn't pay off.