The pancake on its own is thin and mostly air at the edges. Rice flour, a little coconut milk and a spoon of sugar in a fermented batter, cooked without oil in a pan. That is 138 for one. Compare that to a thosai at 170 or a piece of roti prata at 300 with curry, and appam is the light option at the Indian stall.
The toppings are a different story. The pasar malam version comes with a spoon of grated coconut at about 55, and a pour of gula melaka syrup at about 60 per spoon. Two appam with coconut and syrup is about 380, and two with sugar and a slab of margarine, which some stalls do, is close to 400. The version with a whole egg cracked in the middle is about 210 per piece but it has 9g of protein, which is a better trade.
The size varies. A small pasar malam appam is about 40g and 110 calories. A large restaurant appam served with curry or sothi is closer to 80g and 220. Restaurant appam with a bowl of chicken curry is about 450 for two pieces, which is a full meal.