Sorting Computer Memory/RAM

So there are a bunch of different types of RAM out there and I often see the same price being offered for all types of it (besides RAMBUS). They can't all be worth $14-15 per pound, can they? What makes one better than the other?

Here is a bunch of what I've found (the Horizontal are gold, the vertical are tin):
i.imgur.com/EffNL.jpg (Can someone repost this below? I haven't been here long enough to post links)

Where does the value from these chips come from? Is it all in the fingers? In the IC chips?

Are tin sticks worth the same as modern SDRAM sticks because they are populated with more chips on them? Would the flat or double sided EDO's be worth more?

Thanks in advance. I tried searching the forums and could not find an equivalent thread (First post!)

(Can someone repost this below? I haven't been here long enough to post links)

I can't help but think the older and higher quality it is, the thicker the plating would be, but like Mike said, they seem to just pay one price for it. That's another good reason to look first for better than scrap price, before you scrap it. Some of the older stuff has no tags, and the numbers don't always tell you much. I usually fire mine up before tearing it down to see exactly what's in it as far as MB , Mhz etc. I looked at an old motherboard today and did a google search for the number, didn't see any sold but saw 2 for sale, one $195 and one $245. They might not get those prices but the one at $245, I looked at his completed listings and he seems to get his price on most all his listings. I also recently scrapped one that later saw it sells regularly at around $130