The most expensive shampoo I can get my hands on is Philip B Russian Amber Imperial Shampoo, and at $140us, (that's $170 for the Australian viewers).
The big question is does it work?
Yes, and no.
Yes, it made the hair feel amazing and silky smooth not to mention the beautiful smell. Yes it did make the hair feel a million dollars.
And no, as a hairstylist it is so rich and made the hair feel so smooth and silky it did in fact make it hard to style and to give the hair body and bounce.
Best for: coarse, chemically treated hair, curly hair.
Not for: fine hair.
For that kind of money, I could come around to your house and shampoo your hair myself.