So in theory you are correct, but the reality on the ground is that 96gb in a box is getting to be pretty standard now.

Also the other thing to remember is that the standard java GCs dont reliably work under all workloads above 2-4GB. You can make a 8gb or 16gb heap work, but if you hit a full-compaction your JVM will go MIA for MINUTES at a time. So you can't even scale to a 16gb ram heap.

The 512GB is for the previous customers who do in fact use heaps of that size.