We offer 100% trade-in value, for people who wish to upgrade their violin, (normal wear & tear).
Such as the case of younger players, who need to exchange instruments for size, such as exchanging a 1/2 size violin for a 3/4 violin. We don’t really have a formal policy, but will usually take the matter situation by situation. We have always managed to negotiate with parents, as a matter of fact, we’ve been told my way can end up costing a lot less, than badly maintained, overpriced, rentals.
We do not rent small violins in our shop, as it would seem impossible to maintain the quality of the instruments. We have found the kids have better violins to use, by trying to maintain a generous purchase & trade-up system. We have violins, in stock, in all small sizes. As an example, in cases where someone has held a small violin briefly, and comes back clean, in perfect shape, ready to go back out, we have asked parents for little more than the cost of a fresh set of strings & a bow re-hair. If someone is upgrading in quality, as well as size, we have always been able to work something out, and generally make parents quite happy!