I think the AGS price difference between PTS and BTC indicates where the money come from: existing investors, or new investors.
For newer interest, they most likely invest via BTC, existing PTS investors tend to use PTS, if both prices are comparable.
PTS price decreasing from 0.03 to 0.02 btc is at least partially caused by some existing investors converting PTS into BTC to take advantage of the price difference.
This trend will last as long as BTC serves as the better "payment option", however I suspect the source for PTS investment will exhaust first, and the trend will reverse, if AGS remains attractive by then.
JMHO