Promotion fee is also commonly known as introduction fee and agency fee. This kind of fee belongs to service fee, which generally includes management fee/sales fee /R&D fee-service fee. Promotion fee is similar to publicity fee, just like if you have a store, others will help you introduce the things in the store to others, so that others will know that the goods in your store are good and many people will come to buy things. In the profit of selling goods, the person who recommended the introduction should be paid.