Keep in mind that memory chip prices fluctuate almost on a daily basis at the wholesale level.
Similar to oil, gold, currencies, and other commodities, memory chip prices are set bi-weekly.
Influenced by supply and demand, of course, such as what chips a yet to be announced Mac or PC is going to use, but also by earthquakes, tsunamis, etc.
At the retail level, pricing reflects those swings, with some damping and a time lag, much like gasoline prices at the pump in relation to crude oil.
It is not unusual for any given memory sticks to halve (or double) in price within a few months.
So, long story short, there aren't really any not-to-be-missed RAM deals out there.
You will always get another chance soon - and the price is just as likely to be even lower.
You have to analyze whether the RAM you use is likely to be in high demand or over-supplied over the next while.