@9wood if I put a brand new Pro V1 next to a random cheap ball I found in the trees, what differences are we going to see? I think we hardly see any differences. Still people pay a lot more for Pro V1s than for lakeballs, and a lot of Pro V1s are being sold every day. Why do people buy Pro V1s if they do not look that different? Are those people stupid? I don't think so. People buy them for materials, performance, feel and even for the brand and status. Not everything is in the looks.
Interesting, I don't know much about Scotty's, but the 009 seems to be a special model. You are correct that they seem to go for much more than the other models I've seen. This would lead me to believe that it's a limited run/special edition type putter which garners high interested. They type of person who would purchase such a putter likely doesn't care much about the cost as they are more interested in it for the prestige of having it. Still, even though they look very similar to the one you have in your picture, there are going to be some pretty significant differences in the quality of the product.
The Scotty is a collectors item, the SC 009 is a Tour only putter that were/was made for pro's. As @iacas stated, it's a matter of what someone is willing to pay for it, especially with you're talking about collectors.
In terms of physical differences, the 009 is a milled putter I have no idea how the Knight is made. Many pro's have and continue to use the 009, I've yet to see any pro game a Knight. Beyond that, if you look at the details there are a number of physical differences between the two.
There might be other styles of Scotty putters selling for less than the 009 model, but I looked and couldn't find a Scotty Cameron 009 putter that wasn't priced in the thousands of dollars.
Absolutely agree, yet the most I would ever pay for any putter would be $10, but that's just the way I am, and currently my putting game is clicking and therefore I have no need to think about some other putter, especially one of those gimmicky, gawdy ones with those long prongs sticking out the back of it.