¿Cuanto es? O ¿Cuanto esta?
¿Cuánto es? and ¿Cuánto cuesta? are both perfectly valid. The difference is the same as "How much is it?" and "How much does it cost" in English.
¿A cuánto está ...? is something else that can be said, but it is used in slightly different contexts. It is used for a price of something that varies often, and when you want to know what the current price is for today. For example, when changing between different currencies, prices for a barrel of oil, etc.
Ex) ¿A cuánto está el dólar hoy?
Hiya! Can I recommend Paralee's Lesson 1.11 on when to use ser and when to use estar? She's got a great system for remembering which is which. (It's in the Grammar Reference section too!)
I don't know if you can say '¿Cuánto está.....?' but I think you can ask '¿Cuánto es esta camiseta?' to ask how much a shirt costs.
You're asking the value of the shirt, and that's a characteristic, so you need to use 'ser'.
I suspect that 'Cuánto cuesta......?' is the best option, but I'm not sure.