Mine changed a couple times since starting. But now it seems I have a better deal than ever. Too bad I can't afford to spend more $$ on gems or I would take this offer:
10 gems - 10 energy
20 gems - 24 energy
50 gems - 60 energy
20 gems - 32,000 coins
100 gems - 160,000 coins
250 gems - 400,000 coins