you can not compare like this... the examples you give, it is that the customeralready knows their values and ordinary prices outside before they make the purchase. becuase for the drinks and the potatos you named, you can see their price labels anywhere in supermarket. the customer already has the mentality to pay for the higher price... But for this one, if you dont search for it carefully in the beauty shop, you wont know its original price... so it is counted a cheat.
as wat you have mentioned,the product is also available online and other stores
so you can get the price or the value of the product easily from sources other than the salon. It is as easy as what you do to look up for a bottle of liquor or some veges in the supermarket. Sad to say, you are feeling cheated because that Leo is the only source that you heard of this product from and you naively believe that it will be sold at same price anywhere in the world( which is not true in any case). so, please stop complaining. If you feel hard for the money you spent, you should blame yourself ignorant,being not so resourceful and overconfident on your judgement. To be more frankly, you are simply ignorant. there is a famous quote about ignorance "Unintelligent people always look for a scapegoat. - Ernest Bevin"