You mean the price you buy at Circle would "intentionally" lag off a price, say from Bitstamp + or - $1 here and there?
My understanding is they are very similar to Coinbase and you are buying coins directly from them. They have their own buy/sell prices and their revenue is built into those prices.
Hmm, I see. So they create their own buy and sell prices, but are not classified as an exchange, because it's their own coins.
We'll see if they stay "free" after they've gained a large userbase.