Great topic. I think there are a number of factors playing in. First of all, I think people have a predisposed idea of what purpose a knife is supposed to have as a tool and they don't realize the difference between good quality, bad quality and great quality. Second, they are not quite aware of that collecting knives is an established phenomenon and a hobby for a lot of people and the reason we find it interesting is to a big extent because of all the craftmanship that goes into it, which is also a reason for the vast differences in price. It's an interest and a hobby. I think there are several things you can do to make people understand more. You can compare it to a lot of things that people choose to put their money on. Clothes, shoes, tattoos (the best example IMO), jewellery, whatever. An even better thing, I think, is to explain a little bit about it all. You don't have to get her to become a knife enthusiast herself, but explain a little bit about all the different factors that play in and make her realize that knife collecting is a much bigger and more complex topic than she probably knew about. Also try to make her realize why you are so interested in it or at least make her realize that this in fact IS something that's very important to you, wether she understands it of not.