[AndyPatterson]

I don't think it is.

For a start, it's not the lean/agile way to have a large capital cost for your idea. If the idea dies, so does all that money you've wasted.

Secondly, the example given is quite naive in design. You wouldn't serve directly from s3 because of costs so you would serve via caches/cdn; for instance, using aws cdn would cost 85 cents.

Going back to the first point though, you're putting a lot of money at risk.