The most common way of asking how much something costs is ¿Cuánto cuesta?

The vendor will likely answer back with Cuesta + number + currency, or Vale + amount.

Need help with numbers? Learn for the first time, or review how to say 1-1,000,000 in Spanish in the Reference section of this course.

If you think there may be a hidden impuesto (tax) on the service and/or to take a last step to make sure you understand the total price. Say:

If you don't understand the precio (price), don't be shy to ask: ¿Puede escribirlo, por favor? (Could you write it down, please?)