The fundamental principles of copywriting have stayed the same throughout, and those are the very foundation on which Scriptdio PRO sales letters framework is built upon.
While today people prefer sales videos, most people, before making a purchase decision, also read, or at least scan, a sales letter, after they finished watching a video.
Sales letters are so powerful that they can be used even without video. In fact, in a wide range of market niches, very often products are sold with just a sales letter.