Nah. I pay monthly, include monthly pricing. I can probably set up an nginx/varnish instance faster than I can calculate the monthly cost when you're billing by the hour.
Billing is based on usage for load balancers. You can't offer fixed monthly fee as users may consume all of your network or system capacity and pay as if they were using nothing. This is not a sustainable business.
One thing that is nice is the automatic failover (of the routing stack) when a VM or datacenter goes down.