diff --git a/litellm/router.py b/litellm/router.py
index 95c95f86f87..2e256a8ce23 100644
--- a/litellm/router.py
+++ b/litellm/router.py
@@ -615,8 +615,9 @@ RETRY_BREADCRUMB_LIMIT: Final = 4
 # Cost-map keys created by _register_deployment_in_model_cost, which shares one flat
 # namespace with the built-in model catalog. Only a key it created may be evicted, or a
 # deployment whose id names a real model would strip that model's pricing and
-# capabilities for every other deployment of it. delete_deployment gives a key back, so a
-# later catalog refresh that starts serving that name is not treated as a deployment's own.
+# capabilities for every other deployment of it. delete_deployment gives a key back once no
+# live router still serves that id, so a later catalog refresh that starts serving the name
+# is not treated as a deployment's own.
 _DEPLOYMENT_COST_MAP_KEYS: Final[set[str]] = set()  # mutable-ok: ownership of shared cost-map keys
 
 
@@ -9875,7 +9876,11 @@ class Router:
                 _budget_limiter: Final = self._get_router_deployment_budget_limiter()
                 if _budget_limiter is not None:
                     _budget_limiter.unregister_deployment_budget(model_id=id)
-                _DEPLOYMENT_COST_MAP_KEYS.discard(id)
+                if not any(
+                    router is not self and id in router.model_id_to_deployment_index_map
+                    for router in tuple(_live_routers)
+                ):
+                    _DEPLOYMENT_COST_MAP_KEYS.discard(id)
                 try:
                     self._unregister_pre_routing_strategy_for_deployment(
                         deployment=item if isinstance(item, Deployment) else Deployment(**item)
diff --git a/tests/test_litellm/test_router_model_cost_isolation.py b/tests/test_litellm/test_router_model_cost_isolation.py
index 749af1da7c0..c7dca63feb1 100644
--- a/tests/test_litellm/test_router_model_cost_isolation.py
+++ b/tests/test_litellm/test_router_model_cost_isolation.py
@@ -348,6 +348,40 @@ def test_should_give_a_cost_map_key_back_when_the_deployment_is_deleted():
         _restore_model_cost_entries(original)
 
 
+def test_should_keep_the_cost_map_key_while_another_router_still_serves_it():
+    """Two live routers can serve the same deployment id, and the claim is process-wide.
+
+    Releasing it when only one of them drops the deployment would put the survivor back on
+    merging, so the price it just cleared would keep billing.
+    """
+    from litellm.router import _DEPLOYMENT_COST_MAP_KEYS
+
+    model_id = "deployment-served-twice"
+    original = {model_id: litellm.model_cost.get(model_id)}
+    entry = {
+        "model_name": "served-twice",
+        "litellm_params": {"model": "gpt-4o-mini", "mock_response": "ok"},
+        "model_info": {"id": model_id, "input_cost_per_token": 0.005},
+    }
+    first = Router(model_list=[entry])
+    second = Router(model_list=[entry])
+
+    try:
+        assert model_id in _DEPLOYMENT_COST_MAP_KEYS
+
+        assert first.delete_deployment(id=model_id) is not None
+
+        assert model_id in _DEPLOYMENT_COST_MAP_KEYS, (
+            "the claim was released while another router still served the deployment"
+        )
+
+        assert second.delete_deployment(id=model_id) is not None
+        assert model_id not in _DEPLOYMENT_COST_MAP_KEYS
+    finally:
+        _DEPLOYMENT_COST_MAP_KEYS.discard(model_id)
+        _restore_model_cost_entries(original)
+
+
 def test_should_preserve_builtin_pricing_regardless_of_deployment_order():
     """
     The built-in pricing should be preserved no matter which deployment