I'm not really surprised that people can tell when a piece has more more or less work put into it, and the final score reflects that.
Here's some info: my last submission, 'The Third Light' was adapted from my thesis to try to fit a tee. And you guys could spot immediately that this wasn't designed for a tee!
Naturally.
I'm very busy with a lot of personal projects right now, and while I want to keep submitting to threadless frequently, I don't think it's worth it to adapt old work for tees- the score isn't worth the work! I'll stick to original designs from now on.