I've worked as an executive creative director, art director and creative busines realtionship developer since 1997. Including just over a year long stint at Stack Exchange (when stack overflow got too big for its britches) as it's first actual art director... so the citations will be how my businesses or the expectations of the businesses I worked at handled the development of identity based work, like "logos" commonly known as wordmarks or logomarks.
In short, all small studios ranging from 1-5 employees to larger agencies and even as an independent contractor: equity based value was calculated on a projected lifespan of the marks usage, the brands income, its value per impression based in ad buys and media usage, and then very lastly - hours billed for the specific project.
These values help gather a sense of not just your works value, but also how to service and steer your clients use of their new marks so that it is most effective for their own ROI AND ROAS.
Any creative work, is considered "intellectual property" from a legal perspective.
Once you grasp these areas, how much you charge, and the limitations on use you negotiate,and the corresponding fees are appropriate as the agreement indicates.
To forgo any libel, one footwear brand we worked for lacked a strong social media practice, content strategy, staff or service method.
We created a brand, a method and a practice: in exchange for a large fee AND equity.
This is applicable to any size project for any size business.
If the business or brand you work with can't respect or value it's own use of its own marks, dont work with them. You'll meet many better and more valuable clients that will become partners with the practice you build.
Anyone reading this old thread should strongly consider cautionary tales of previous false sense's of trust with businesses like Nike, and creatives like Carol Davidson. It took decades before she was rightfully awarded equity in that business, for her extremely valuable "swoosh" design.