Duck is fattier than chicken before it goes anywhere near a fryer. A piece of fried duck thigh with skin is 337 calories on FatSecret with 76% of that from fat, against 390 for a bigger piece of ayam goreng with more meat. Per gram of meat, duck costs you more. The skin is where it lives: strip it and the same piece is about 220.
The Madura cart version is the one to watch. Nasi bebek Madura comes with rice, a small piece of duck, sambal hitam (a dark, oily shallot sambal), serundeng and a spoon of the duck frying oil poured over the rice. That spoon is 90 calories on its own. The Rp 20,000 to 30,000 plate is about 650, and the duck is the smallest part of it by weight.
Bebek goreng Surabaya style, the Pak Slamet and Purnama type, gives you a bigger piece, a bright red sambal bawang and raw lalapan. The piece is 380 with sambal, and the plate with rice is around 640. The sambal bawang is made with hot oil so a spoon is 55, but the cabbage, cucumber and basil are nearly zero.
The protein is only 22g per piece because a duck thigh is small and a lot of the weight is skin and bone. For the same 380 calories, ayam bakar gives you about 32g protein. Bebek is a flavour order, not a protein order, and that is fine once a week.