Knowledge: The cost of professional piano lesson is about $100 per hour but it depends on the location and the teacher. Also, the cost of professional hair dye varies as it depends on the length. The starting cost is $100 and for very long hair is about $600.

Conversation:
I'm thinking about coloring my hair purple.
That sounds cool. Is it to cover up grey or white hair?
Yes, I'd like to hide my greys in a fun way. Is there anything I should know beforehand?
Well, you can do it yourself, or you can go to a professional hairdresser.
I think I'd rather leave it to professionals! Do you know how much it can cost?

Response: Hmmm, it depends on the hair length. The cost of professional hair dye for short hair starts about $100 and very long hair is about $600.