Pempek is half fish, half tapioca, and that ratio decides the calories. A good Palembang pempek is 195 calories per 100g according to FatSecret with about 13g protein, which is more protein than most fried snacks because the fish is real. The cheap street version with more sago than fish is closer to 220 per 100g and has half the protein. Price tells you: Rp 15,000 to 25,000 for a kapal selam at a proper place, Rp 8,000 at a cart.
Kapal selam is the heaviest single piece because it is 150g of pempek wrapped around a whole egg and deep fried. About 310 calories with 16g protein. Lenjer (the log) cut into slices is about 40 per slice. Adaan (the round fried ball) is 60 each because it is fried from raw and the dough has more oil in it. Pempek kulit (fish skin) is 70 each and the crispiest, which is the warning.
The cuko is the part nobody counts. It is palm sugar, tamarind, garlic and chili boiled down to a dark syrup, and 100ml is about 90 calories, all of it sugar. The bowl you get with your pempek holds more than that, and people top it up. A generous soak of cuko is easily 150 calories, which is more than three small pempek.
A 'pempek campur' plate with 5 small pieces, one kapal selam kecil, bihun and cucumber under cuko is about 550. The pempek is not the problem there, it is the count and the sauce. Pempek rebus (boiled, not fried) is about 30% lower per piece, and some places will do it if you ask.