I tried finding out where the cost is displayed to cancel a hack but I'm not finding it here on the forums. On discord I guess it's 30?

Which is conviently the cost of my remaining transmogrification node upkeep. So now I can test another hacking system...

Hello,

If you try to cancel a hacking operation, you should see a pop-up asking for your confirmation.  The amount of PP this will consume (and how long it will last) should be displayed there (it's 30 PP, the duration is dependend from the game speed).  

Have a nice day :)

I wasn't able to get that pop up. I just had a little message flicker "Don't have enough bandwidth to cancel."