Apple Watch repair or new cost

The best advice is still to get an official quote from Apple, but you can find the non-warranty repair charges at https://support.apple.com/watch/repair/service/pricing/

There are too many variables to answer your question here in Apple Support Communities forums. The cost will depend on where you live (currency, etc) and whether you have AppleCare+ cover on your watch. Use link Contact Apple Support to have Apple check cover and give an official quote for repair.