Depending on the user base, it wouldn't be farfetched to just buy the lowest end RAM version and upgrade the RAM yourself. When you're spending $30k on RAM... it's probably worth some time to shop around. Whether Apple supports it... well that's another question.

Also, if you only NEED 32GB of RAM, then don't buy a Mac Pro. This is just like buying a Xeon motherboard anywhere else and only putting 16GB of RAM into it. Sure, you can do that, but it's a waste of money.