Why do you rarely see the same shampoo in your local shop, as you do in your local hair salon and why can there be a wide price differential?
It is not for me to say what you should and should not find in your usual shop-bought shampoo though it may be helpful to understand what some of the main ingredients in main-stream shampoos are, so you can decide for yourself.
One of the first in the ingredient list of many shampoos is Sodium Lauryl Sulfate (SLS) This ingredient is not harmful, if used briefly and rinsed from the skin, as with shampoos and soaps. Many reports say that products that stay on the skin for any length of time shouldn’t exceed 1 percent concentration of SLS. That said, the only reason this ingredient is included, is to make whatever you are using appear creamy, to create lather, so as to give the impression that whatever you are using, is doing a good job. SLS may also strip natural oils from the hair - and SLS is derived from petroleum or coconut or palm oil. If SLS is high on the ingredient listing, you are buying lather!
Mineral oils may be used as a lubricant and can help to detangle and mositurise but mineral oil is not going to do much in the nourishing department. Mineral oil is often used to pad out the advertised nourishing oils, so it is important to check how fare down the ingredient list the really good stuff appears. Let us say Avocado oil or Argan Oil - if it is way down the list, it has probably been thinned out with mineral oil.
Parabens are basically, a preservative and have been in use for a long time. The most commonly used Parabens in cosmetics are Methylparaben, Propylparaben, Butylparaben, and Ethylparaben. However, these may be disguised a bit as they can also be listed as "Alkyl Parahydroxybenzoates". It is not, as yet, proven but they may result in hormone issues (some Parabens may mimic the activity of estrogen) but I would stress that there is, as yet, no fully proven link to cancer or to serious health issues. Parabens may cause skin irritation, though as long as the hair is properly rinsed after using Paraben products, at this time, and as long as they are down the ingredient tree, then there is not too much to get worried about.
Silicones are a type of mineral that are used in both shampoos and, of course, conditioners with the intention of making the hair appear soft and silky. Silicones, however, act like a plastic coating on your hair; this keeps moisture out, rather than letting it in. Repeated use of silicone can cause a build up on the hair strands which, over time, can make the hair brittle and dull.
PEG (Polyethylene Glycol) is used to produce a creamy texture to shampoos and conditioners. They do very little, if anything, for you hair. The jury is still out on the effect of PEG on your health as studies on reactions to PEG are few and far between and those that have been made, have arrived at mixed conclusions. If you wish to read more on the subject, you may wish to read this (rather dry and lengthy) article.
Sodium Chloride is often used to make shampoo thicker, to give the impression of a a really nice treatment for your hair. It isn't. Sodium Chloride is salt. The stuff you use on your chips or to dry out meat or fish in cooking some tasty recipes. You can imagine, therefore, what this can do to your hair. Enough said.
Perhaps you may wish to looking at salon style hair products, which either do not use any of the above ingredients or if they do, in only minimal amounts.