I have an 04 Camry (6 cyl) I took to the shop & was told I broke A gear in the trans case. I'm having him fix it but is $2300 a fair price for Rebuilt one ?

Yes. That is about the going rate to have a rebuilt transmission installed. I looked at several sites and some say as high as $3200. But at 72k miles is unusual, even at 15 years old to have it fail. But to clarify, is this an automatic or manual? You don't say trim of your Camry

72,000 miles is a lot if it has been 70,000 miles of abuse- when you buy a used car from a dealer you roll the dice- you lost this time- snake eyes- NOW what do you do? bite the bullet and try to get it running- then sell it- I would not trust a rebuilt tranny- next time buy a used car from the individual who owned it since new- and when you take the test drive, let the owner drive it so you can observe how he/she drives- this is no guarantee, but it sure gives you better odds before you hand over the cash-

Now THAT is good advice.