Please read till the end before answer.
I would like to spend 150-200$ for preparing a quick demo, but it is hard to understand which package I need and if they are really worth the money.
furthermore any project can change drammaticaly from prototype to the final version and some packages may became worthless later on, while others became needed.
Having an upfront cost like that really stops me from buying anything. I always wait till the last moment, and buy everything as later in time as I can, even important things that could change the feeling of the game.
On the contrary I immediately download and use every free content provided by Epic and other developers.
so what I’m proposing is something similar to what you do with UE4,
everything is free from the start, but each project should have a “licence costs” which is the sum of the costs of each packages used within that project. Now, before being able to ship the game, you must first cover the “licence costs” of the packages.
Of course I’m aware that it would be hard to release C++/blueprints source code, and then identify that they were actually coming from the marketplace and not made from scratch.
However it could be implemented just as an addition puchase option, in the first case you pay upfront and you get the source code (like now), otherwise you get the binary but you pay only when shipping.
I don’t really know much about other type of contents (3d models, animation, etc…) so I don’t know I would handle those scenarios, but still…
you released the engine source code and you must have ways of detecting if someone didn’t pay your fees. if you could figure it out something similar to protect content creators too, it would be a win-win situation.
For example, in order to build a package for the shipping stage you could require an internet connection in order to check for protected contents (something similar to what youtube does for copyright).
In this way contents creators would have a much richer base to sell their product, and more from even a single user since if I’m shipping 2 different games with the same bought package it would require 2 different purchases.
As for the consumers, they could include everything from the marketplace from the start, being able to quick prototyping and being much more phrone to keep already used packages when reaching the shipping stage.
as a second suggestion I noticed that you financialy help game creators, but I think that if you could buy some contents already in your marketplace and release it for free for everyone that could help too (of course after reaching an agreements with the content creator).