Filesystems, Disks and Memory

Nowadays the fastest SSDs achieve read-speeds of between 1500 MB/s to 1900 MB/s. Let's say that two such SSDs in RAID 0 achieve roughly double the throughput, ie 3000 MB/s. That is only half an order of magnitude removed from RAM ((10)^(1/2) * 3000 = 10.000), very broadly speaking.
So for the price of about a twentieth of that of RAM (comparing dollar figure per GB for both RAM and SSD), I can get something which is performance-wise close to RAM.
Is anyone familiar with such a setup? Is what I have just theorised even correct?

Possible bottlenecks include your RAID controller, your bus, and your northbridge. Don't think you'd get performance even close to theoretical.

Hardware RAID0 is always faster than a single disk because you can step the reads and writes across the two disks simultaneously. However, I have never come across a case where throughput was doubled. Typically you will get something like a 50% increase in throughput.

Software RAID0 can provide throughput improvement but typically less than hardware RAID0.

Thank you for your responses. Would you then recommend RAID 0 with disks of equal read/write speed?

Depends for what purpose. It's hard to speak in generalities.

I was wondering about the situation when having two disks in RAID 0 setup, with one distinctly faster than the other. Would the faster disk be overkill, because the speed gain is not utilised to its full advantage? In other words, would software have to be written to use the faster disk more often?

I don't really see the point of doing so. Performance would be lower and inconsistent. Something smarter than simple mirroring or striping would be needed to get the advantages of both.