Elbow supports and braces come in different models, sizes and materials depending on the manufacturer. Depending on your needs, different types may be better. Depending on these features, prices can range from about 8 euros to about 100 euros.
If you want to compare prices, it is always better to go by the prices of specific types, materials and application.
There are many different places where you can buy an elbow support. Online you can find them in different manufacturers' websites or special orthopaedic websites as well as in normal websites like Amazon.com or eBay. If you want to buy the product in a physical shop, you can find the brace in orthopaedic or sports shops.