http://www.alibaba.com/showroom/price-of-sodium-benzoate.htm... http://www.alibaba.com/showroom/cinnamon-price.html
Looks like the prices are surprisingly similar, though cinnamon is, if anything, more expensive. Additionally, I'd imagine that if sodium benzoate is the active ingredient, you'd need less of it to get the job done.
Apparently, cinnamon can be used as a vehicle for moving sodium benzoate to wherever it needs to be.
Alibaba is notorious for scammers. I know two startups that have lost around $20,000 each on material suppliers listed there who send something cheaper (usually completely different) than what has been requested upon payment. It's usually the orders that are around $1000 that Chinese chemical/raw materials supply companies selectively scam on.