My last four cards...
3 capacity - 120,000 iMG - passed on this one
5 capacity - 200,000 iMG - passed on these too
1 capacity - 40,000 iMG. I bought this one becasue it was more affordable
3 capacity - 240,000 iMG ?!? This was my next draw.
I looked at my logs and brain capacity cost seems to increase exponentially. I apparently just lost 160,000 iMG by not knowing to buy the 5 capacity card. *cry* I only got 1M points so that's a loss of 16% of my iMG from a non-obvious mistake.
Looking at my logs I had one increase after 4 points, the next after 3. Buy your brain capacity in bulk, folks!