User blog comment:Oioiaussie/Buy playgrounds? A common misconception!/@comment-5177487-20120620125510

How about gems? They have a ridiculously long ROI, but the Emerald produces 3,000 (750x4) coins in 8 hours while the VFT's would only produce 1,800 (9x200) in the same space. The Ruby at 2,400 (600x4) also out earns the VFT's.

Granted, you have more collections, but a 9x9 arrangement of VFT's would produce 5,400 a day with 3 perfect cycles, while a single Emerald would produce 6,000 if you managed to collect 8 times (16 hour wake time).

Hmmm... I suppose it comes down to how much work you're willing to put in, lol. I have to check my village at least every hour to empty out my Dino dens, so the gems are working better for now.