How much will it cost to replace my headphone jack in a macbook pro?

this happened to me and I was able to fix it on my own. Try rapidly inserting and removing the headphone in and out of the jack. Hopefully it will flip the internal toggle switch that is stuck. I gave this advice to someone here a few days ago and it worked for them as well.

The official Apple cure is a new logic board, so it behooves you to follow shldr's sage advice. Next step is to prevent it happening again.

The port is digital and held to high dimensional standards. Many headphone and speakers are NOT held to those tolerences. It is the plug's tip-to-shoulder distance that is the critical dimension. I have a pair of no-name speakers whose plug fits perfectly; a name-brand pair of head phones have a plug that's too long. Here's how to avoid problems when inserting a headphone plug:

1) have the audio source running before attaching headphones or external speakers

2) Have the headphones on your head (or external speakers turned on)

3) insert the plug until you hear audio from both speakers with normal balance, then STOP pushing

The plug will have enough tension on it to hold.

Here is how the name-brand headphones that had a too-long tip-to-shoulder distance look when properly attached to an older MBP I have:

Yes, in that position the phones gave proper balance and separation. Note there is nearly 1/16-inch clearance between the plug's stop shoulder and the computer case.

That worked for me also,after weeks of restarting etc. I blew air into the port first then rammed headphone jack a couple times. Et voila Rock and Roll. i had forgotten how good imac sounds.