The ROI you mention would seem to imply a return on financial investment, but that is not the limiting factor in Farmville moving forward, because the typical high level user has tons of money sitting in the bank, but has maximized their land use, so wants the highest return on acreage with little regard to the return on financial investment.

In this case the numbers definitely seem to point towards the peas if increasing a bankroll is the primary goal.  Regularly planted peas provide $2112 per 12 days, which is $176/day which is $11/mini-square/day as the top seed.

I don’t know the rules enough for how this compares to Goats @ $27/mini-square/day or Olive Trees @ $28/mini-square/day, but absent limitations it would seem like a farm 100% full of Olive Trees would be the biggest earner for any given space (again we don’t care about return on financial investment, but instead space, because we have more money than we can spend).

The math is different for someone starting out and who hasn’t filled their space, because you can plant 1 area of peas or 7 of soybeans for the same price, and 7 soybeans pays more.  Additionally when space is not limited compounding needs to factor in when comparing different harvest rates.

Anyway, I don’t have it all figured out, and I personally am playing and designing my farm for more enjoyment based goals rather than just the fastest millions and highest levels.  I just wanted to bring up a couple of the assumptions that need to be specified for economic analysis as well as differentiate between the scenarios of Space-Filled-And-Lots-Of-Money and Still-Have-Empty-Space-But-Limited-Money.