Given the latencies shown in the article, if it's 30x that it'd probably take a few hundred ms to render. I'd view that as unacceptably slow; your milage may vary. Also, I suspect 30x that is optimistic for a complex site; it is a single small table.
400m sessions a month doesn't really sound like that much...
If you spend 20K in developer time to optimize for few hundred/month savings you are not going to be saving much (and that is not counting the cost of maintaining that extra code over time)
