I have been wondering this recently. It was the convention that if you wanted to keep costs down, try to keep the memory bus size down as low as possible. Still remember the awful Radeon 9200 SE - 64bit data bus that strangled an already slow GPU.
Heck, I have a phone with a 16bit memory bus for instance. The high(ish) clock rate only makes up the difference slightly.
But with general prices on all components going up, it might not be such a big factor any more.
HBM migght make sense for higher end products which can free up space for the lower end that will never use the tech.
Eh I feel like the memory bus width thing was more a case of binning memory controllers and the like.
Designing a part with a wide bus and putting the traces down on the board is what I would expect to be the easy part these days (surely).
But yield, yield comes for us all.
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