Most of the “top notch” assets / programs / plugins that I use come in a variety of packages or support levels… or a separate support package altogether. Doing something similar on a “marketplace” such as the Unity store or UE marketplace is nigh impossible, however, they can be sold on the company’s site as long as they use an e-commerce package to sell it.
Lite versions: Cheap, cannot use commercially, no support (basically, an educational license)
Full version: Mid Range price (affordable for non-), Can be used commercially, no support
Pro version: Expensive, Can be used commercially, support provided