typically a server with 16Gb of RAM is powered by quad-processors intel xeon quad cores, or the equivalent AMDs.
That's a bad idea; you should probably run away from any host that wants to sell you such an inefficient configuration. 16GB is 8 2GB DIMMs; putting that in a 2-socket server is no problem. Even 16 2GB DIMMs should be no problem.
well yes, and no. i guess it depends on your needs and the applications you run on the server. if you do virtualization, a 2 socket server should be ok. I was thinking of HPC or datamining
there are many cheap quad and dual-core Xeons and Opterons. I use 1.9Ghz low-power quad-core Opterons, which cost around $256 each. You pay a large premium (in power or money or both) for the last few clock cycles. If you need more ram than CPU, which is usually the case for me, you can save quite a lot.
so yes, RAM is cheap, but RAM is just a fractional cost. at $8000, a web hoster needs to compute in costs of stocks, loan costs, so $800/mo is a reasonable price.
if you're really low on budget and need 16Gb (I guess it's for virtualization ?), look for "7310 hosting" in google, and then boost the RAM to 16Gb. You should be able to find one at around $650