[Evilhomer]

Yeah i was just taking a bit of a stab in the dark, therefore i did say turn 50+, not turn 50 (I admit they were exaggerated by more then i thought, must be influenced by playing the cb mod so much). However your numbers are not correct either:
pop:10000 at start, assuming no fort and no other scale modifiers:
pop at 50 (growth 3): 10000*1.006^50=13486
income/turn=13486*0.01*1.06=143 gold

pop at 50 (death 3): 10000*0.994^50=7401
income/turn=7401*0.01*0.94=70 gold

gold increase due to growth = 104 %. I dunno what you mean by the percentage being less or more depending on population since the income is directly proportional to you population, so you end up with the same % in the end. 1/4 income was obviously a bit exaggerated but money after upkeep might be cut that way. Anyway i think the benefit of taking growth in a mega game like this is pretty clear.