I think Expedia does not have up to date inventory on the price you are seeing. The fare search claims there is 1 seat left at that price, but when you actually click through to the purchase screen, the price jumps to 1672.20. The same price that is showing on delta.com. So it appears the 1 seat left in the bucket has actually been sold and is no longer available, but the Expedia fare search engine does not realize that yet and still thinks it is available. When you go to purchase the ticket, it does a live check on the bucket inventory and realizes it is no longer there, thus producing the higher fare with a different fare class.

I see flights out of IND for $1100 that do not require an overnight layover at CDG on the return.