Nvidia buys the memory it uses on its GPUs, same as all other ASICs.

To give some context, Intel started making DRAM, I think they were actually the company that came up with modern memory techniques. They exited the market and pursued a more lucrative moat with CPUs.

Nvidia does not make RAM

That doesn't excuse them from wrecking the market for ordinary person.

NVIDIA produces memory?

Fabless AFAIK. And that's the actual problem - drawing up CAD diagrams doesn't help if the factories are fully booked out.

A state of the art GPU is much harder to design & produce at scale and than an internal ASIC.