Bought one when I was newer because I liked the look. Wasn't the best cutter, I think they may be thinner now though. I don't believe your cousin when they say some get 1k+.
Furthermore, I have never seen an sg2 rainbow. From what I know, there are blue 2, and I believe VG10's are a recent edition.
Personally, don't understand the worth of collecting since they aren't exactly rare, and I think there are better performing and looking knives out there. However, I never "collect" anything just because it has unique attributes or is rare. It has to be a really good product for me as well.
I do think they are pretty though. I would own an ironwood rainbow again if fit and finish and cutting performance was improved.
my old one:
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