What is cost of transmission replacement on this car- automatic

It all depends on where you have it done. I just replaced mine at the dealer and the original quote for a rebuilt thru dealer was 3,400$. I made the service manager ask for assistance from Honda and they gave it to me for $2,800, but my car also had 155K. If yours is younger, you might get more help from Honda. It also came with a 3yr/36,000 warranty. Main reason I went with dealer. So far so good, runs okay.