Category 4 (CAT 4) refers to the tickets costs for Qatar citizens. As we can see, qataris have access to a huge discount in every stages of the cup.
The prices are showed in Qatari Riyal, the local fiat currency. For better calculating the costs we can use 3,64 QAR = 1 USD.
I am not surprised by this, and such discounts are given to the citizens of the host nation every time they stage the world cup. And in case of Qatar, it should not matter much. Do you know why? Because Qatar do have only around 300,000 citizens (and all of them may not be interested in watching football). Millions of tickets are available for sale and the number of tickets is greater than the number of Qatari citizens (only around 10% of the population of Qatar is made up of nationals). Some of the stadiums in Qatar can accommodate the entire Qatari national population in one go.