We're all competitors, and therefore you're asking a question that many would answer in doublespeak. But, I will tell you that people are selling assets (Menus, Particles, Sprites, Sounds, Voices), for 5-10x the price you suggested, on the Unity asset store, for example, which has Terms that you may be interested in because the asset can only be used on Unity projects for example. And as an example/tip, you could sell your Pooling (or Preloader) script, or SoundManager script, or Menu class script, etc. separately.
Use Unity 2017, 2018, or 2019. Don't worry about "security" and "updates". They're fake. Don't be a slave to updates. Stop updating your phone, computer/windows, everything!
