RAM is disproportionately expensive on leased/managed servers; afaik it's just the pricing model that hosting companies established in the past (when RAM accounted for more of the total hardware cost compared to now), and the industry has stuck with it.

We run 32 GB on our DB servers ... may be going to 64 GB soon.

Way back in May 2007, Facebook reported using 200 16GB memcached servers, and suggested 32GB servers were soon on the way:

http://article.gmane.org/gmane.comp.web.cache.memcached/3224

Big, popular services don't skimp when fighting latency.

With high-end server motherboards having as many as 16 memory slots and 8GB DIMMs existing on the market, it's certainly possible. http://supermicro.com/products/motherboard/Xeon1333/5400/X7D...

I've been playing with 6 boxes, 32 gigs each.

read this from mysqlperformanceblog http://www.mysqlperformanceblog.com/2008/08/04/128gb-or-ram-...

Our main box has 32gb ...