SSDs are cheap in terms of $/IOPS. In fact they are about a hundred times cheaper than HDDs (Crucial C300 128GB: $250 for 50k IOPS vs. entry-level 7200RPM HDD: $60 for 120 IOPS or so).
People, stop assuming that $/GB is the only metric that matters.
I wonder if $/GB matters when people are selling VMs (like say linode), I don't know how many Virtual Machines are put into one server but if you are doing 16gb per VM and depending on the RAID usage as well it might start to add up.
I also don't know if this is still a problem but there was a worry about limited writes on SSDs and if normal harddrive lifetimes are greater than that of an SSD by a significant amount I could see why it would be a problem.
People, stop assuming that $/GB is the only metric that matters.