The short answer is no, having your ring sized does not change the value. Jewelry valuations are typically based on the insurance replacement cost of the item (what would it cost to recreate your ring brand new) however if the structure of the ring has to be modified dramatically then in some instances it can affect the cost to reproduce it. A simple example would be sizing a ring either up or down more than 3 or 4 sizes. Even this shouldn’t change valuations much unless the ring features a very wide and heavy shank.