Thanks! and yep, that is correct. If you already own 2.x, you can just keep it, however no more updates will be made to it. If you want to upgrade to 3.x, you can do so by paying the 15$ difference. Also, 3.x is not backwards compatible with 2.x prefabs, since most of the optimizations come from the way data is serialized. So if you have some cloth set up in 2.x for your project and don´t want to re-make it, it would be a good idea to stick with 2.x and only use 3.x for new projects you're about to start. Warnings about this backwards incompatibility will be written all over the asset description, update description, readme and manuals, though.