Years ago, before Amazon as you put it "created cloud computing", the running joke was that they made a loss on every sale but made up for it in volume. So yes, basically, for years on end when they were just a retailer they were propped up making a substantial loss for years on end.
Perhaps you should rephrase this as "for years on end when they were a startup, they were losing money while growing revenues and gaining market penetration".
Every year from 2003 to 2011 amazon posted a net profit, with a very small loss in 2012 (which wasn't really a good year for anyone).
They didn't launch EC2 as a product until 2006, so clearly they were making money before that, and it's not a significant percentage of their revenue even now. AMZN recorded $2.5Bn in "other" revenue in 2012 (this includes AWS, but also includes credit card agreements and advertising services, so the AWS number is somewhat less than the total), and just over $61Bn in total revenue. Even assigning all "other" revenue to AWS means that it nets out at barely 4% of total revenue.