That’s why you don’t see 384

2080 Ti, 3090, 4090.

or 512-but memory bus anymore

We haven’t seen them since we moved to GDDR6. Simply because the signal integrity and power requirements makes it quite unreasonable.

find other ways to make up the performance for games

Lack of DRAM scaling is the reason why we are where we are. Computational power has grown much faster than bandwidth.

Nvidia has had around a generation of advantage in bandwidth efficiency/utilization since Maxwell over AMD. Surprise surprise, one generation after AMD they as well have to resort to larger caches to substitute for bandwidth.

A 512 bit G6 bus (which isn’t realistic to begin with), would not have given 4090 enough bandwidth over 3090. To keep up with the growth in computational power.

In the retail market yes, that’s what small scale smuggling is for. Getting several shipping containers to fill your DC with, will be harder however.

total capacity has continued to increase even with the decline of orders.

Probably funded by the CCP to build out excess capacity as a buffer against potential future sanctions.