how much to rebuild V6 automatic transmission 2005 Honda accord

Hello, The cost of rebuild is tied to the parts that must be replaced. Once the transmission is torn down, it will require testing and measurements of various parts, and then there are some that are replaced without regard to condition like clutch discs.

As a side note, I'd recommend getting a second opinion just in case. Anything is possible, but it's not tremendously "common" for a 2005 Honda V6 automatic transaxle to have a failure under normal conditions.