YYZ-CMH has always been crazy expensive, and I'm not really sure why.
I used to go there frequently, and I often ended up flying to CIN instead and then driving to CMH. It's about a 2 hour drive, and the flight is half the price ... right now you can get a RT for your dates, for $1068 (which is still a lot for such a short distance, but it's cheaper than the CMH direct).