So, what you prefer then: Pay 50 $ for a product and have it per-tittle or pay 300 $ or more and have it for life?
That is why, it would be better, if there is an option for people to choose. Adding these two types of license, and let the buyer choose what he wants and need. is the most fair.
Buying models, textures, plugins, etc, is like hiring people to do that for you. And when you hire someone to do that work, you pay them, right? Ok, But, do you think, that you will pay them just once, and they will be working for you for life? Or is just for that tittle?