Questo means "this" and quello means "that", and both agree with their noun - questo/questa/questi/queste. To ask a price, use quanto costa? for one thing and quanto costano? for several.
Examples
- Quanto costa questa camicia?
- How much is this shirt?
- Prendo quello, non questo.
- I'll take that one, not this one.
- Quanto costano queste scarpe?
- How much are these shoes?
The mistake to avoid
Costa or costano follows the THING, not you - two shoes costano.
Where this fits in
Food & ordering, Italian A1: Order at a café or restaurant, ask for the bill, and talk about basic food and drink.