Sales and lead generation is huge, I buy quite a few themes from ThemeForest, you seriously going to hunt around the net to 100 different sites where each author has 10 themes. Marketing has a cost and keeping an audience is very valuable
I've purchased a few themes as well, however every time I've gone to do it I usually contact the author via email first and offer to buy the theme directly from him for 30-40% off. I save money, they get more money, we all win.
Ethically borderline IMHO if you used the marketplace to find the theme first. If you found the author first, and saw they offered themes in a certain market after, it would be more acceptable to contact the author directly. You're essentially cutting out the marketplace from the transaction which damages their business model.
