To date, I have not gone with a premium theme. I’ve always built upon free or open-source selections using a child theme for my customization. There are a few premiums though that I really would consider purchasing, such as Parallax, Divi and one that has recently caught my eye, Vertex….
As of this post, this site sports a customized child theme of Pinboard for WordPress, a responsive masonry grid design by One Designs. I’ve used Pinboard in the past as a parent theme for a WordPress version of my Legacy design, which I created using HTML5, CSS3 and AJAX back when they were still new kids on the block.