This is so true, the world has changed greatly and not everyone has gotten the memo. I saw a really cool device made by Texas Memory systems which was a "ram disk" that was all ram with disk backing, and when you lost power it flushed to disk. I wanted something that worked better for a storage paradigm and designed/invented a network accessible memory appliance[1]. Basically using ethernet packets you could store 8K integrity protected chunks right there on the network. Initially I wanted to use a typical low power CPU with a bunch of DRAM attached but the CPU bottleneck got in the way, so we redesigned/rebuilt it out of FPGAs so that it had a couple of terabytes of RAID protected RAM in an appliance with a very simple network protocol for storing and fetching 8K blocks out of what was essentially a linear address space. Two of these on different power subsystems provided all of the fault tolerance you needed and you could have a terabyte of 'structured' data live from the moment your computer booted (made for very fast recovery from reboot).
If I understand the question, then yes. When you consider the amount of cache memory in clustered systems which is all holding the same stuff in every independent machine. Using it simply as a victim cache for a block storage device penciled out to a pretty significant improvement.
It gets even better with 64 bit address spaces and a bit of kernel code to 'fault in' from the device.
[1] https://www.google.com/patents/US8316074