When asking how much something costs, you can use the following:
Quanto costa? How much does it cost?
Quanto costano? How much do they cost?
Qual’è il prezzo? What is the price?
If you like the price, these are good expressions for you:
Cheap / inexpensive / low cost - economico / conveniente / poco caro / poco costoso
Good price - buon prezzo / ottimo prezzo
Low price - basso costo / prezzo basso / prezzo ridotto
Affordable - buon mercato
Reasonable price - prezzo ragionevole
Dirt cheap - da due soldi / di pocco prezzo
On the cheap - al risparmio
However, if you think it is expensive, you can say:
Expensive - costoso / caro
Very expensive - molto costoso / molto caro
Pricey / steep - salato e.g. pay through the nose for something - pagare salato
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