OK, to be upfront here... I don't code, so I have NO idea about how much work it takes to write or maintain a plugin. So any comments below are strictly as a user.
It seems to me that a large number of the available plugins are just 'nice to have' things. I'm referring to things like 'Emergency Stop buttons', ability to make the webcam full screen, custom status displays on the printer, etc. Plugins that do add nice functionality, but nothing that a person couldn't live without. That is not meant to belittle them in any way. But, it does mean that I would assume most of the users would not bother loading and installing them if there was any cost associated with them.
Then, you have the plugins like OctoLapse. This is obviously a very complicated and powerful plugin, that clearly took considerable time to write, upgrade, and maintain. I do feel that it would be reasonable to charge a fee (premium) for something as robust as it.
There was discussion about having 'lite' and 'full' versions. Wouldn't that actually be far more work for the creator? I'm not so sure that would be such a great idea. However, I DO feel that any 'premium' plugins should allow some kind of a 'free trial' period, just to make sure that it works for the buyer.
As far as the 'simpler' plugins go.... How many of them would you guys estimate get created by user requests? If a coder just decides to write one for himself (for personal use, just for fun, or whatever), and then make it available to everyone, I'm thinking they shouldn't expect any payment beyond the occasional tips. However, if someone requests a new plugin (as I recently did with the time stamp on the timelapse), well maybe that would be the time to ask the requester to pay a nominal fee, with the understanding that the plugin would still go into the public domain for others to use. Do you think that may be a viable option to get a little extra something for your work?
So to summarize... I would support the idea of 'premium' plugins, for plugins that truly are premium. As long as they come with some kind of a trial period, or a refund option if it wasn't workable for a user for some reason. And I would also fully support the idea of charging a nominal fee for 'basic' plugins that are requested by an individual, while still allowing those plugins to be used by others once they are created.