teuer
expensive
Having a high price; costing a lot of money.
Wohnen in der Innenstadt ist sehr teuer geworden.
Living in the city center has become very expensive.

expensive
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expensive
Having a high price; costing a lot of money.
Wohnen in der Innenstadt ist sehr teuer geworden.
Living in the city center has become very expensive.

When 'teuer' (expensive) is declined before a noun, the 'e' before the ending often drops. For example, you say 'ein teures Auto' (an expensive car), not 'ein teueres Auto'.
Sie hat sich ein teures Kleid für die Hochzeit gekauft.
She bought herself an expensive dress for the wedding.
The expression 'jemanden teuer zu stehen kommen' (to cost someone dearly) means that an action has serious negative consequences. The person who bears the consequences is in the dative.
Der kleine Fehler in der Planung kam die Firma teuer zu stehen.
The small mistake in the planning cost the company dearly.
The meaning 'geliebt' (loved) or 'wertvoll' (valuable) is outdated and today is used only in poetic or very solemn language, for example in 'ein teurer Freund' (a dear friend) or 'ein teurer Schwur' (a solemn oath). It is not used this way in everyday language.
In dem alten Brief nannte er sie seine „teure Freundin“.
In the old letter, he called her his 'dear friend'.
nice / dear
'lieb' and 'teuer' can both have to do with personal value and affection, especially in fixed or elevated expressions. In normal everyday language, however, the difference is large: 'lieb' usually means friendly, nice, or loved. 'teuer' almost always means that something costs a lot of money. The emotional meaning of 'teuer' is rare today and sounds elevated or old-fashioned. The words can be confused especially in expressions like 'lieb und teuer' (dear and precious). There, it is not about the price, but about something being very important to someone.

Für Sofia ist dieser Ring teuer, obwohl er nur wenig Geld gekostet hat.
For Sofia, this ring is precious, even though it cost very little money.
Das alte Foto ist mir lieb und teuer, weil es meine Großeltern zeigt.
The old photo is dear and precious to me because it shows my grandparents.