So I've been playing for quite some time now (currently at level 30)... but I still have serious trouble farming enough coins to purchase the latest production machinery such as Smelter,
Juice Press, Ice Cream Maker, and Net Maker, which really screws me up when I get the orders for their products. I've farming up a large amount of blackberries now since they have fairly high selling price per unit.
I've been playing solo as a casual player (too busy with other netgames to play Derby), so slowly-farming coins is hardly an option for me... I've trying to get there as patiently as I could but it's very hard to do so when there's no end of these in sight.
In short, what I sought is:
Products I can sell with the highest time to money per unit ratio.
Products that can be sold at the highest price per unit (@Level 30 or more).
A list of pricing of the production buildings.
...and other ways to generate revenue without taking too much time in general.