It appears as if BUF is the lowest, with CLE a close second.

I am finding RT "walk-up" fares (no advance purchase) from BUF in the low $600s, from CLE in the mid $600s. With a 1-week advance purchase, the BUF fares drop to the mid-$400s, and with 2-week advance they drop to the low $200s.

So if your consultant is going on a regular basis, it would seem as if you could save a lot by buying 2-week advance purchase tickets and then changing them if he/she doesn't go. And remember, if you use Southwest, they have no penalty for changes.

Feel free to email me if you have more questions or need help.