fix example costs (Reference openrouter)

Author: SNHuan

easyagent/config/config_example.yaml

@@ -24,9 +24,9 @@ models:
     api_key: your-key
     # cost: model metadata for litellm cost calculation
     cost:
-      input_cost_per_token: 0.0000003
-      output_cost_per_token: 0.00000252
-      max_tokens: 8192              # model's max capability
+      input_cost_per_token: 0.0000005    # $0.50 / 1M tokens
+      output_cost_per_token: 0.000003    # $3.00 / 1M tokens
+      max_tokens: 8192
       max_input_tokens: 1048576
       max_output_tokens: 8192
     # kwargs: API call parameters