So much for cheap ideology spamming. 
I haven't fully tested this yet, but it appears that whenever you choose an ideological trait in one table the costs increase on ALL tables.
NOTE: ALL TESTING DONE ON INSANE MAP WITH ABUNDANT STARS/PLANETS - NORMAL GAME SPEED
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I was a little surprised to see that the first ideological trait cost 10 points given some of the chatter. However, once the first ideological trait is chosen, it then becomes 20 to raise it again on that table while the other two tables are now at 15 each for their initial trait.
Later on, I had cause to chose the initial trait in a separate ideological table. The next trait on this table was also increased by 10, while the other two tables were each increased by 5.
Doing some more testing, it appears this pattern repeats itself. Again at least on an Insane Map with abundant stars/planets. For each trait you chose, the cost to get the next one on that table goes up by 10 points while the costs on the other two tables go up by 5. I haven't checked out other map sizes or by number of stars/planets so it may be variable for them. However, I suspect the system of increasing the other tables when increasing one is universal, regardless of the way it's calculated.
So for those of you who were saying that it was far too easy to spam out all three ideological tables... Perhaps not as much anymore. 