Once again want to say that I like the feature a lot. It needs just a bit more improvement though.
Some customization options I already mentioned. Most important one is to allow either species-specific or hetero vs auto-troph-specific costs.
I also wander how the multiplier is calculated. Seems like its change is proportional to the ratio between current population and desired one. It would be nice to figure the rate of change of population into the equation somehow. So that if the population grows quickly, then the costs should grow quickly and if it begins to stabilize, then the costs should stabilize or even go down a bit.