The best way to stretch you're budget in the bahamas is to eat local food from local restaurants.

The 2 main areas for fresh local food are the Fish Fry at Arawak Cay and Potters Cay.

The Fish Fry is a small "village" of bahamian owned restaurants serving up the freshest fish and local dishes at the best prices in town.  There are a dozen or venues, from Twin Brothers, Seafood Haven and Deep Creek, to Goldies Bar, serving a concoction known as SKY JUICE.    You'll find home made Daiquri's, fresh conch salad, and even entertainment on the weekends.  

Potters Cay is a bit more casual.  It consists of a couple dozen fish shacks, some selling fresh fish, and some selling freshly cooked fish, conch fritters, conch chowder and made to order conch salad.   You can grab a cold beer and sit down with the locals to a game or two of dominos.   This is VERY down to earth.  The roadway cuts thru the market, and it can get very crowded.  Some find it part of the charm, some find it a bit scary.  Any way you see it.  The food is fresh and cheap. 

You can also find moderately priced items at any of the Chinese Restaurants.  Double Dragons has several locations.  Additionally, Domino's pizza delivers to your hotel lobby, and has a great deal for about $20.  No more expensive than back home. 

Lunch time, you'll find the lunch ladies selling native lunch and soups from there vans and car trunks.  They are usually located in the parking lots across from the main hotels (Atlantis, Radisson and Breezes), and also downtown by the Straw Market by the Wharf.  Full meals start at $7.   Hearty Soups from $5.   Mac and Cheese for $1.

Imperial Takeaway, located in front of the British Colonial Hilton servers hamburgers/cheeseburgers for $3, Cracked Conch $6 and a $3 breakfast.  Cafe Skan's downtown also has cheap breakfast and lunch as well.