Robert is frustrated that his iMac doesn't have enough RAM. 32GB is just not enough for editing 4K video. Leo says that it could be a hardware limitation. The most he can install is 4 to 8 GB sticks. He could invest in the Mac Pro instead, but Leo thinks its terrible. What is Apple up to? Leo says nobody knows. The iMac is faster, better and more reliable than the Mac Pro according to Leo. Will Apple change their tune? No. They want him to buy a Mac Pro if he wants that much RAM. So they have no reason to improve the RAM capacity in the iMac.
Robert can try Other World Computing at MacSales.com. They're better on prices anyway, and they'll sell him the 16GB sticks. But they're not cheap, even there.