In your opinion, is expensive, professional salon-quality shampoo better than your average drugstore/supermarket quality shampoo?

I thought of this question today because i was at the hairdresser, and they had some professional quality shampoo 40% off, original price $20 per bottle (and no, i did not buy it). I was wondering if, in the opinion of the Fluther collective, an expensive salon shampoo is any better than a regular brand, the kind that can be bought at a supermarket or drugstore, for example (just some random examples) a brand like Pantene, Fructis, Herbal Essence, etc.

Do you think your hair can look it’s best with an inexpensive shampoo, or do you think an expensive, salon quality shampoo (the kind only available at a salon or professional store) is worth the extra cost?