I have a handful of pets that do indeed have CWs in their treasure. The items were very fitting for them. Maybe a few I could do without. Maybe. But the characters that the pets are based on are very near and dear to me, so I don't regret having spent the funds on them.
I look at it this way - if I'm willing to spend 300M for a single item for one pet, then why shouldn't I spend ~75M on another item for another pet?
For the longest time, I completely ignored CWs in terms of pet treasure. And I mostly still do. For things like, the sheer cost of it, and the very real possibility of simply not being able to have an item (private). For me I think it's better to just pretend CWs don't exist when working on treasure.
However, I did manage to fall down the slippery slope of putting CWs in one pet treasure, because at the time, there weren't many of that themed CW, so I thought it was doable. Well, basically, I guess the theme got popular because more and more were made. It became more than I ever expected or could handle so I kinda lost my wind on collecting it... xD'