HBM is a stack of DRAMs, so there is no “instead”.

The vias to enable stacking is a significant amount of the die area.

	▲	saltcured 3 hours ago \| parent [-]
		If they're talking about production capacity, that is some product of die area and process steps, right? It doesn't have to be 3x die area, just 3x lower factory throughput for the same number of functioning memory bits.