How recent should your comparable prices be

A price from several years ago can be a historical reference, but it does not necessarily describe today's market.

Prioritise recent data, especially for products still in production, digital gear, equipment with frequent revisions and categories strongly affected by current new-product pricing.

For rare or discontinued models you may need to widen the observation window. In that case, compare several years and determine whether there is a genuine trend or whether the differences mainly reflect the condition of individual examples.

Do not apply an automatic appreciation percentage. Market evidence comes first; any time adjustment comes second.