It had half a terabyte of RAM, sand they’re not saying what it cost. It could also be that the demand for that model was so low, they wouldn’t list it anymore. If you needed that configuration, you could probably special order it.

No consumer needs more than 16/32GB of RAM on a Mac. Some gamers are pushing 64GB RAM, but I haven’t heard of anything but fringe benefits for doing so. The people who need 512GB of RAM are doing some high end video production — think like Pixar type applications. Making these extremely detailed models and rendering them in 4K for a movie. That kind of thing.

Macs have unified RAM and a special MLX framework for AI purposes tailored to their M chips, which makes it possible running full sized ChatGPT/Gemini/Deepseek level LLMs locally without serious limitations. You can also join 4 macs using lightning port and make a cluster for LLM/image/video generator model. It’s a real bang for buck stuff compared to other platforms for personal use. So they disappeared because they are mostly sold out, even after price increase.