You should also install the TTCMac add-on. It's a separate application that you run before you log in to ESO. Run it and it prompts you to select your server (EU or NA). Hit 'Import' and it pulls in the current TTC data. Then, just run ESO like normal.
I used to do something similar on mac since I didn't want an unknown app running in the background - You can use the built-in scripting program called Automator to automatically download the latest info from ttc, then extract it to the TTC addon folder. Alternatively, a bash/shell script could work just as well if you know a bit more about the UNIX terminal.You are also able to download these price files manually from the website afaik so you do not even need to run the client.exe to get the prices.
For EU server PC
Else change the eu to us
Put that downloaded price file to your live/AddOns/TamrielTradeCenter folder overwriting the old one AND make sure ESO was not running at the time you did this!!!
It looks like someone wrote a Mac app for TTC,
However, they mention sharing the "Documents" folder and not just the ESO live folder. So not sure what's going on there.
Even now the game is not recognizing the add on when it's running. I would have expected it to tell me I'm missing a dependency or it's out of date or something. There doesn't look to me a MAC and PC specific zip to download from TTC. Maybe I need to do something to kick start it?