Fabian is shopping at a nearby supermarket. He wants to buy 5 kilograms of apples, 3 packs of sugar, and 500 grams of walnuts. One kilogram of apples costs $2, and one kilogram of walnuts costs $6. One pack of sugar is $1 cheaper than one kilogram of apples. How much Fabian needs to pay for the items he wants to buy?
Please reason step by step, and put your final answer within \boxed{}.
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