After all this very valid, very sensible feedback, you're commenting here saying "you need to be thinking out of the box" and trying to justify all the time, money and energy you spent on those t-shirts. Your customers are complaining because they want you to succeed. If they didn't care about you, they'd just cancel the subscription and move on. And your response to it is "nah, what we did was right" and not "yeah, maybe we shouldn't have spent all that resources on a stupid t-shirt that nobody wanted"?
I just don't get it. And what are you gonna do when you hit 50K members? Are you planning to send an entire wardrobe (from undies to a suit) to all your 50K customers (assuming IF you ever hit that many customers)?