I've spent 2-3 months in Empire 3 & 2 and have not found a single base like that. I did find a lot of bases with 5-6k+ of oil, and plenty of 500-600k+ food and gold, but even with league bonuses it didn't add up. Add no opponent message and higher stress levels on top of that. Bullying bases in lower leagues is a lot more efficient, and I can net a lot more resources in the same amount of time than being in higher league.