alt Hacker NewsI have, but only a few times. For one-offs, it's been when I've come across a paid model that included a particular technique or mechanism involved that I really liked and hadn't seen before. In those cases, it's worth the cost just to get a working example of it I can pick apart, rather than flail around trying to replicate it from scratch.
The other time was paying for a subscription to this[1] Thangs profile, which was more or less the same. I love making stuff using these techniques, and having access to all of his paid models really helped me get familiar with it using working examples. I mainly make my own designs now instead, but still pay for the subscription out of pure appreciation.