Govinda's Lunch on 305 Schermerhorn St. in Brooklyn (basement of the Hare Krishna temple) is excellent and quite affordable. Their lunch buffet has $3, $5, and $8 options, all healthy and very filling. They have plenty of great Bengali food as well as various others.
Govinda's Vegetarian Grill on 111-14 101 Avenue in South Richmond Hill, Queens (unconnected to the above-mentioned restaurant, despite the similar name) also has fantastic and affordable food. Theirs tends to lean toward Bhojpuri cuisine with Caribbean influence, reflective of the heavy West Indian Hindustani population in the area. They also have a number of super delicious meat-analogue dishes.
Those are two you don't want to miss.