Actually both of you are saying the same: Collecting has nothing to do with logic. It is only that each of you comes to another conclusion.
In the end you cannot really be an investor if you insist on enforcing logic on LEGO collecting, you rather have to accept that the whole business model of LEGO investing relies on people making "not financially advisable" buying decisions which you make your profit from.
I for my part am kind of an anti-consumerist, hardly spending any more money than really necessary on anything, and I already wonder about 99 % of other people's everyday buying decisions, be it food, shoes, cars or toys. So, of course I'd never start collecting myself because this would be pretty much the opposite of my philosophy. Still, I am very happy about the fact that there are hundreds of millions of people out there who DO like to spend a lot of money on all kinds of stuff they do and don't need (one of them being LEGO sets). Without them the whole economy would not work. So, my own philosophical conviction aside, as an investor I love other people's unreasonable consumption very, very much. If it's their free will to hand me their hard-earned money I won't stop them from doing so. They "are willing to pay", and I am willing to cash in. Logical or illogical, abvisable or unadvisable - I just don't care.