I have been to Bang On easily about a dozen times in the last year for friends' pregnancy announcements, coworker gifts etc. I frequented the one in Vancouver when I lived there quite a bit. Not that my perpetuity of showing up makes a difference which is the only thing that irks me - I spend roughly $60-$80 each time I'm there but, no one cares. I know - I'm expecting too much, need to take my own self down a notch.
It's not cheap but, in theory, if you're making your own you are doing it for sentimental/personal reasons and it will truly be unique.
I did try to save myself a few shekels on an order by buying Joe Fresh Tshirts I got pre-approval for through email to the location and my text saved as an image that they charge a flat fee for and I actually saw the sales persons lip curl in disgust at my (in my mind) thriftiness.
Basically, your custom shirt will most likely be $50 incl tax but it most likely will be done in about 20 mins from initial conversation.