I almost always purchase a premium theme, they stand out and are feature-rich compared to free ones. I love the simplicity of free ones but premium themes can be more tailored and fit certain niches. There are also so many to choose from and so many talented theme developers. I have never requested a custom theme though personally, those are very expensive and outside of my price range. I don't think I would pay more than $60 for a theme, at least for a while. I do think that themes, specifically for XenForo, have gotten really expensive. I remember when they were around $25-40 and now most of the nice ones I've seen are $60-100