Qatar and Dubai Duty Free are the most expensive

I frequently travel outside my country for various conference and workshops. A couple  of times I have visited various duty-free shops around the world. Most of the times when I go outside my transit is either in Qatar or Dubai

But very frequently I have visited the Qatar duty free and  Dubai Duty free may be 6 to 8 times. One thing that I notice while purchasing good at such markets are the prices, in these so call shopping tax free shops, they have the most expensive good priced where in most cases its the most expensive price  anywhere else. It is exactly double the market value. I think it is not fair in so many context as a traveler may not know and selling the same goods even exceeding the MRP is not correct whether you have the prices tag or not.
It is something like taking advantage of traveler who has no idea and selling him or her off her money for the same goods that is readily available at a lower cost.

They are suppose to be duty free that means, they are suppose to be cheap in context of market price but in reality with all the twinkling and glitz the customer are robbed off their money.

I think in one way its  cheating the customer with the literal meaning and just creating a big fuss about the overall concept of DUTY FREE   

When I was in Abu Dhabhi UAE,  I notice something that the prices of alcohol in UAE were way cheap at the local store. Though you need a licence to buy alcohol but it was way cheaper, I mean to say a Chivas cost around USD 20 where as the same would cost me USD 40 at the Duty free.

Even in Qatar where i had a transit the situation was the same, the prices are whooping high where there should have been relatively  less. 

I was very spectical as this is duty free country where the government has declared tax free in major import sector and still the prices are so high.

Why should a traveler who is  willing to buy or create business should suffer ?