Hair is stubbornly individual. A shampoo that transformed one person's scalp does nothing at all for the next, and no amount of experience behind this counter changes that.
So wherever a product exists in a small size we stock the small size, and we will steer you to it first. It costs more per millilitre. It costs a great deal less than a five hundred millilitre bottle you stop using in week two.
For a few of the treatments we decant into small pots so you can take one application home. There is no charge for those and we do it about a dozen times a week.
We are aware this is not how a shop maximises a sale. It is how a shop gets somebody back in six weeks, which we would rather have.