How much should a timing belt replacement cost at a Honda dealership for a 2010 Honda Accord?

Our car is in for some work where they already have the engine pulled. They said it would cost $750 to replace the timing belt (nearing 100k miles) since they already have the engine out, rather than the $1,200 if we brought it later to get it done. This seems really expensive to me.

My wife spoke with them so I haven't been able to find out whether that is just for the timing belt, or if it is also water pump/other belts too.

That should include the water pump too. It ran me a grand for my 00 Accord. That's a dealer price.

If the repair includes the water pump as well the cost is within reason.

Well parts and labor with the engine out. The 1200 would be more labor with the engine in the car. So their about right on price. Remember they go by book labor rate which is legal in all states so even if it takes them an hour they go by that book rate which might be 3 hours to do the job plus the parts