Update pricing.mdx (#20604)

added example of pricing

Author: kathayl

src/content/docs/ai-gateway/reference/pricing.mdx

@@ -32,6 +32,8 @@ Persistent logs are available on all plans, with a free allocation for both free
 
 Allocations are based on the total logs stored across all gateways. For guidance on managing or deleting logs, please see our [documentation](/ai-gateway/observability/logging).
 
+For example, if you are a Workers Paid plan user storing 300,000 logs, you will be charged for the excess 100,000 logs (300,000 total logs - 200,000 free logs), resulting in an $8/month charge.
+
 ## Logpush
 
 Logpush is only available on the Workers Paid plan.