The cost of a stock silencer for a Royal Enfield motorcycle can vary depending on the specific model and region. Prices can also change over time due to factors like inflation, availability, and location. It's recommended to check with authorized Royal Enfield dealers or spare parts retailers in your area to get accurate and up-to-date pricing information for the stock silencer of your Royal Enfield motorcycle. They will be able to provide you with the most accurate cost based on your specific requirements and location.