Where are you located, and in what country are you seeing this term?
1 - Assuming you are referring to Japan as the exporter, the type of material being exported from Japan varies tremendously based on which country is doing the importing: for example Europe, Singapore, UAE, China, USA, and Canada all have very different import requirements that heavily influence the process. Of course, the taste, interests, budgets, etc. of the importer and their market also affects what type of material is being imported.
2 - It also depends what you're looking at/referring to in your post -- there are many different ways in which 'bonsai' is practiced. If you're looking at the corkscrews in pots that show up at Home Depot, then the answer to your question is yes, these are being produced in large quantities, but not usually in Japan. But if you're looking at material directed at a more specialized audience then the answer to your question is no, bonsai production in Japan is very distributed across nurseries, professionals and hobbyists, and it's rare to see any one person producing a batch larger than a few hundred units of any given species (a tray or 2 is much more common).