Some people don't care in where they write; $1 notepad is just fine for them. But sometimes, this same person is very particular in what they wear; hence, for example, they buy a very expensive jeans at $100. So let's ask them, "What the hell is wrong with a $30 jeans?"
In a nutshell, different people have different ways in manifesting their sense of egoism.
There is proven benefit to dressing reasonably well. You look better and people treat you better. Cheap clothing is also generally a false economy: the more expensive stuff lasts longer, at least for men's clothing.
None of these clear-cut advantages apply to silly fashion accessories like pens or notepads.
In a nutshell, different people have different ways in manifesting their sense of egoism.
P.S. I am not a moleskine user.