> in many situations 5GB is considerably more expensive then 1TB of disk
How do you figure? This amount of memory sets me back for less than double the cost of disk space. But *only* if looking at ECC RAM versus cheap & big SATA storage. Go to SAS, as used in many servers, and the scale is more like 1:1.
And that's not even considering RAID, where net capacity is not 100%
Of course, in many environments, you need to get RAM and disks from your server vendor, and they mark up prices arbitrarily ... so your numbers can come out completely different.