diff --git a/langchain/callbacks/openai_info.py b/langchain/callbacks/openai_info.py
index 9b0af085..e8d2f3b6 100644
--- a/langchain/callbacks/openai_info.py
+++ b/langchain/callbacks/openai_info.py
@@ -26,26 +26,34 @@ MODEL_COST_PER_1K_TOKENS = {
     "code-davinci-002": 0.02,
     "ada-finetuned": 0.0016,
     "babbage-finetuned": 0.0024,
-    "curie-finetuned": 0.0120,
-    "davinci-finetuned": 0.1200,
+    "curie-finetuned": 0.012,
+    "davinci-finetuned": 0.12,
 }
 
 
+def standardize_model_name(
+    model_name: str,
+    is_completion: bool = False,
+) -> str:
+    model_name = model_name.lower()
+    if "ft-" in model_name:
+        return model_name.split(":")[0] + "-finetuned"
+    elif is_completion and model_name.startswith("gpt-4"):
+        return model_name + "-completion"
+    else:
+        return model_name
+
+
 def get_openai_token_cost_for_model(
     model_name: str, num_tokens: int, is_completion: bool = False
 ) -> float:
-    # handling finetuned models
-    if "ft-" in model_name:
-        model_name = f"{model_name.split(':')[0]}-finetuned"
-
-    suffix = "-completion" if is_completion and model_name.startswith("gpt-4") else ""
-    model = model_name.lower() + suffix
-    if model not in MODEL_COST_PER_1K_TOKENS:
+    model_name = standardize_model_name(model_name, is_completion=is_completion)
+    if model_name not in MODEL_COST_PER_1K_TOKENS:
         raise ValueError(
             f"Unknown model: {model_name}. Please provide a valid OpenAI model name."
             "Known models are: " + ", ".join(MODEL_COST_PER_1K_TOKENS.keys())
         )
-    return MODEL_COST_PER_1K_TOKENS[model] * num_tokens / 1000
+    return MODEL_COST_PER_1K_TOKENS[model_name] * num_tokens / 1000
 
 
 class OpenAICallbackHandler(BaseCallbackHandler):
@@ -91,8 +99,8 @@ class OpenAICallbackHandler(BaseCallbackHandler):
         token_usage = response.llm_output["token_usage"]
         completion_tokens = token_usage.get("completion_tokens", 0)
         prompt_tokens = token_usage.get("prompt_tokens", 0)
-        model_name = response.llm_output.get("model_name")
-        if model_name and model_name in MODEL_COST_PER_1K_TOKENS:
+        model_name = standardize_model_name(response.llm_output.get("model_name", ""))
+        if model_name in MODEL_COST_PER_1K_TOKENS:
             completion_cost = get_openai_token_cost_for_model(
                 model_name, completion_tokens, is_completion=True
             )
diff --git a/tests/unit_tests/callbacks/test_openai_info.py b/tests/unit_tests/callbacks/test_openai_info.py
index c7348821..19b55424 100644
--- a/tests/unit_tests/callbacks/test_openai_info.py
+++ b/tests/unit_tests/callbacks/test_openai_info.py
@@ -44,3 +44,19 @@ def test_on_llm_end_custom_model(handler: OpenAICallbackHandler) -> None:
     )
     handler.on_llm_end(response)
     assert handler.total_cost == 0
+
+
+def test_on_llm_end_finetuned_model(handler: OpenAICallbackHandler) -> None:
+    response = LLMResult(
+        generations=[],
+        llm_output={
+            "token_usage": {
+                "prompt_tokens": 2,
+                "completion_tokens": 1,
+                "total_tokens": 3,
+            },
+            "model_name": "ada:ft-your-org:custom-model-name-2022-02-15-04-21-04",
+        },
+    )
+    handler.on_llm_end(response)
+    assert handler.total_cost > 0