Royalties are paid for each individual item that the toy manufacturer sells to a retailer. Sales samples and such are likely to be excluded. So, contract negotiations are very important. The more expensive the item and the more a manufacturer sells, the greater the royalty income for the inventor. Inventors can make a lot of money, but licensing an item is not so easy.
Toy manufacturers see thousands of product submissions from professional inventors each year.
Additionally, most toy companies have their own internal development staff making it more difficult to come up with new and continually exciting products. Professional toy development houses are often turned down on many products before they get one or more licensed. Even so, professional inventors are more than two hundred times as likely to deliver a product to a toy manufacturer that has any likelihood of being marketed than the average clever amateur inventor. As a result, the majority of toy manufacturers will not work directly with the general public. They will only look at products presented to them by professionals.