Digital refractometers with extended warranties are available from a variety of manufacturers. The cost of the extended warranty will depend on the specific model and features of the refractometer. Generally, extended warranties can range from a few hundred dollars to several thousand dollars. It is important to research the specific model and features of the refractometer to determine the cost of the extended warranty. Additionally, it is important to read the terms and conditions of the extended warranty to ensure that it meets the needs of the user.