12/14/16 still doesn't seem beefy enough to have that great of a draw to spend knowledge on and to rebuild the harvesters for.
In fact I find myself never needing to get those bonus harvesters.
If perhaps it were more like this... 10/15/20
the 10 would actually make you wish you had more, driving you to buy the next level for that nice boost of resources for that area. However if that still wasn't enough, then tier three looks just as pleasing as well.
Or perhaps something like this to give that extra push to actually spend your worthwhile knowledge on the resources.... 7/14/28
To be honest, a minor improvement isn't seen worthwhile. anything<4 = hard to be interested in. o.O! I think perhaps its a math ideal where the mind thinks anything below 4 isn't as great, but 5 can mean rounding up so it gets that + spark. =P Also x1.5 or x2 seems more idealistic for a logical improvement for resource gain.
All I'm saying is, right now it doesn't seem worthwhile, nor needed to make you actually think you need to go through for decision making on spending where you need your knowledge.