Autodesk charges if you want to render more than 50 images. Vectorworks has said that cloud storage is cheap, but cloud computing is expensive -- and so will be charging its customers (eventually) for processing 3D drawings into 2D plans online. So, how much does the cloud cost?
In summer 2011, Cycle Computing delivered a 30,000-core cloud for under $1,300/hour, using Amazon Web Services. [source]
For an end user, employing the service for a few seconds, it's going to cost just $1.80 or so. For a Cloud Services Reseller like Autodesk and Vectorworks, it's going to cost $1,300 an hour or $11 million a year, should the service be fully utilized by thousands and millions of CAD customers.
(Naturally, the $1,300/hr pricetag doesn't necessarily apply directly to CAD renderings; it's a number we can work with. And yes, I did invent the new "cloud services reseller" moniker.)