kostbar
precious / valuable
Of high material value; expensive and valuable.
Die Königin trug ein kostbares Diadem aus Platin und Diamanten.
The queen wore a precious diadem made of platinum and diamonds.

precious / valuable
Loading your saved state.
precious / valuable
Of high material value; expensive and valuable.
Die Königin trug ein kostbares Diadem aus Platin und Diamanten.
The queen wore a precious diadem made of platinum and diamonds.

The word 'kostbar' is derived from the noun 'die Kosten' (costs). The ending '-bar' turns it into an adjective that describes something as having high costs, meaning that it is very valuable.
Dieser Ring ist ein kostbares Erbstück meiner Großmutter.
This ring is a precious heirloom from my grandmother.
You can tell whether 'kostbar' is meant materially or ideally from the noun. If it refers to objects like jewelry or art, it is about monetary value. If it refers to abstract things like time or memories, it is about emotional value.
Er bewahrt die kostbaren Vasen in einer Vitrine auf.
He keeps the precious vases in a display case.
In its material meaning, 'kostbar' is often connected with luxury goods. Typical combinations are 'kostbarer Schmuck' (precious jewelry), 'kostbare Edelsteine' (precious gemstones), or 'ein kostbares Gemälde' (a valuable painting).
Im Museum werden sehr kostbare Manuskripte aus dem Mittelalter ausgestellt.
Very valuable manuscripts from the Middle Ages are displayed in the museum.
When it is about ideal value, 'kostbar' often describes intangible things. Common phrases are 'kostbare Zeit' (precious time), 'kostbare Erinnerungen' (precious memories), or 'ein kostbarer Augenblick' (a precious moment).
Danke für den Tipp, er war wirklich kostbar für mein Projekt.
Thanks for the tip; it was really valuable for my project.
important
'wichtig' and 'kostbar' can both show that something has high value. The difference lies in the focus: 'wichtig' is used when something has great importance for a goal, a decision, or a situation. 'kostbar' is used when something is very valuable, either because it is expensive or because it means a lot emotionally. Time, memories, or jewelry can be 'kostbar'. A piece of information or an appointment is more likely to be 'wichtig'. Memory aid: 'wichtig' helps with or decides something; 'kostbar' is valuable and should be protected.

Die alten Fotos meiner Großeltern sind für meine Familie sehr kostbar.
The old photos of my grandparents are very precious to my family.
Beim Arztgespräch ist es wichtig, alle Beschwerden genau zu nennen.
During a doctor's appointment, it is important to describe all symptoms precisely.