(idiomatic) An informal greeting, not requiring a literal response. In form a question, and thus followed by a question mark. Typical responses include:

unspecified number / what number

(interrogative) What amount or quantity (of something stated or implied). / (specifically, when referring to the cost of an item) What amount of money.

(interrogative) To what degree; to what extent.

(UK, slang, obsolete) you what? huh?

Synonym of what about

(idiomatic, colloquial) Informal greeting roughly equivalent to How are you? or How's it going?

The knowledge and skill to be able to (do something correctly).

how much does it cost?

(idiomatic, informal) Why; why is it; for what reason or purpose; due to what cause?