You'll spend more time finding buyers than it's worth for the extra gold.

Set a reasonable price. What would you pay to have your alts ran through if you didn't box? Find long term repeat customers. Ask them to schedule ahead of time. It'll become a quick daily for a lot more gold than dailies give you.

I don't think you'll be able to find much business for more than 200g per run.

If I were going to put time into doing something like this, I'd target people leveling in icecrown (high 70's) and charge them for runs through normal ToC. I'd also target fresh 80 DK's and Paladin for daily runs in H.ToC for the edge of ruin. These are the players who are desperate to catch up in the arms race. These are the players paying 1k for titan-steel mace when they could be paying you for the Edge of Ruin drop. You can charge them for other gear drops, or make gold sharding it while you run them for the edge.