I visited Kolkata aeons back. I remember having Puchka, Jhal Muri, Kathi Roll and Sattu (drink).
I regard Mumbai as the street food capital of India. Truly amazing spread of street food. Check out my notes on 100 Mumbai Street Food.
Here are more items picked up from various blogs on the Net:
Phuchka,
Jhal Muri
Kathi Roll
Sattu
Churmur
Keemar Doi Bora (Dahi vada)
Shingara (Samosa)
Chanar Jilipi (a different jalebi)
Aloo Kabli (potato sabji chaat)
Bhaja (fritters or bhajiyas)
Aloo Dum Luchi or Luchi Aloo (puri with bhaaji, luchi is poori)
Mughlai Paratha
Cutlet
Chop
Ghugni Chaat (dried white peas)
I would agree that Kolkata rates are very low. Similar to Ahmedabad. Maybe also to Chennai. Mumbai street food is also inexpensive -- though not comparable with other cheaper cities.
Sorry. I am vegetarian so I have included only vegetarian items.