I have a bureau with 4 drawers full of Lego pieces. I hit the Tag sales, and buy bag fulls, that would cost you 100's of dollars, for 10 or 15 bucks. I can tell you that looking at all the pictures shown so far, I would say they are all parts that are standard. They may have come with a particular kit, but you can guy them a from Lego, just be prepared for sticker shock. When you see a normal block going for $.025 cents, you can see why I grab bags of these when I can. There has to be interesting parts now though, and one swipe through the bag, with a well trained eye will tell you that instantly. I could guess at the over all size of these beauties by certain parts.
Since these bags of Legos are for the most part used by snot nosed kids, they go right into the sink, in very hot water and dish washing anti bacterial detergent, and are washed, and hosed down. It's nice that they are not affected by water, and clean up so well.
They also glue with regular model cement, so if you build something really special, you can make it permanent.