I have one gigabyte of ram right now and its nothing special but other people always talk about Good ram and bad also i see 1 gig sticks prices range massively is this because some ram is so much better than other ram ( i know about DDR1-DDR2-DDR3).
I guess you could say that RAM is like cars, some are better than others, some are more expensive, and there are lots of different manufacturers. There are high performance cars that cost more yet, and the same can be said for RAM.
You can find less expensive modules and may never have any problems, but if you are running dual channel. overclocking, video editing, or 3d imaging then the RAM starts becoming a lot more critical.
If you have more specific questions feel free to add them.
I have found that ram is the only pc component that has a somewhat stable price over the years. Just the other day, I went to newegg, and looked at all the pc components that I bought for the system I built last year.. the price of everything dropped significantly in the last year... However, the ram I purchased actually cost more since last year.