Memory prices might be on the upswing up in the next few weeks. Lots of memory manufacturers are still bleeding money, and as production lines are shut, memory prices next year could rocket up. But that's a medium-term issue.
For nowm prices on DDR2, especially 2GB modules are likely to move up in the next month or so. That’s memory for the older MacBook/Pro and Mac Pro 2006-2008.
Prices on 2GB DDR3 modules are very likely to head up by 10-20%, possibly more (MacBook Pro or Mac Pro Nehalem). For Mac Pro Nehalem owners [review] with the dual-CPU model, it’s a no-brainer: go straight to 12GB or 16GB, it’s a fraction of the system price. MacBook Pro owners [review] can go to 6GB or 8GB, and should, if you’re using it for digital photography.
Prices on 4G DDR3 for the newest Mac Pro should remain stable, perhaps even trending down over the next several months. It’s the 2GB parts that are at issue.
OWC is a good place to get memory for any model of Mac.