Historically, GPUs have improved in efficiency fast enough that people retired their hardware in way less than 5 years.
Also, historically the top of the line fabs were focused on CPUs, not GPUs. That has not been true for a generation, so it's not really clear if the depreciation speed will be maintained.
> Historically, GPUs have improved in efficiency fast enough that people retired their hardware in way less than 5 years.
This was a time when chip transistor cost was decreasing rapidly. A few years earlier even RAM cost was decreasing quickly. But these times are over now. For example, the PlayStation 5 (where the GPU is the main cost), which launched five years ago, even increased in price! This is historically unprecedented.
Most price/performance progress is nowadays made via better GPU architecture instead, but these architectures are already pretty mature, so the room for improvement is limited.
Given that the price per transistor (which TSMC & Co are charging) has decreased ever more slowly in recent years, I assume it will eventually come almost to a halt.
By the way, this is strictly speaking compatible with Moore's law, as it is only about transistors per chip area, not price. Of course the price per chip area was historically approximately constant, which meant exponentially increasing transistor density implied exponentially decreasing transistor price.
> This was a time when chip transistor cost was decreasing rapidly.
GPUs were actually mostly playing catch-up. They were progressively becoming more expensive parts that could afford being built on more advanced fabs.
And I'll have to point, "advanced fabs" is a completely post-Moore's law concept. Moore's law is about literally the number of transistors on the most economic package. Not any bullshit about area density that marketing people invented on the last decade (you can go read the paper). With Moore's law, the cheapest fab improves quickly enough that it beats whatever more advanced fabs existed before you can even finish designing a product.
Also, historically the top of the line fabs were focused on CPUs, not GPUs. That has not been true for a generation, so it's not really clear if the depreciation speed will be maintained.