Adding sentence.

Author: Oxyjun

src/content/partials/workers/durable_objects_pricing.mdx

@@ -4,7 +4,7 @@
 
 import { Markdown } from "~/components";
 
-[Durable Objects](/durable-objects/) are only available on the [Workers Paid plan](/workers/platform/pricing/#workers).
+[Durable Objects](/durable-objects/) are only available on the [Workers Paid plan](/workers/platform/pricing/#workers), and are billed while the Durable Object is active.
 
 |                      | Paid plan                                                                                                                               |
 | -------------------- | --------------------------------------------------------------------------------------------------------------------------------------- |