There is an aspect of cost yes, and there is an aspect of improving public image for many celebrities.
But I can assure you that there are hundreds of thousands of people who merely enjoy the look and feel of faux fur and don't equate it to an antiquated and barbaric process. I'm one of them.
As far as saving the environment, we should all do our share. But I don't think it's necessarily hypocritical to not contribute - not killing animals is a way of life and something you do not because other people do it, but because you believe deep down in the practice
(heck, I'm sure there are posers, people who dive into a way of life without research merely to sit on a high horse and be morally 'superior' from their standpoint. It's the same as many people of religion who fail to understand their religion but base their evaluation of others on it daily, though there are those who dedicate their time to understanding what they practice and challenging what they are taught to believe). Even if it was proven to me that wearing fur was ethically acceptable, I still wouldn't wear it as I don't believe I'm capable of spilling blood for any reason other than the deepest need for survival which hopefully I shall never encounter.
I'm sure many people only buy faux to appease those around them. Mindsets are changing however and many people genuinely believe (and in my opinion, with reason) that fur, although a beautiful look can be imitated relatively successfully by man without the need for animal slaughter.
But people do need to understand why they aren't wearing fur and not just to sway public opinion favourably.