Look at it this way. Say there will be 500K coins out in circulation by end of POW. And GAW expects another 500K of dumping from customers at paybase. Why would they eat into their own reserves to reward dumpers (GAW is still losing $7 of their reserve per coin to the dumpers)... when they can just buoy their own customer base at the $20 promised? The miner/dumpers will have to take their low sell bids off of the exchanges and take them to paybase to get $20 per coin. Removing the low sell bids from the exchanges can increase the value of the remaining coins on the exchanges.
So you're saying that instead of spending 500x7 = 3.5 million USD to buy up coins now, GAW would rather spend 500 x 20 = 10 million to buy up the same coins later?
The only way this could possibly make sense - and someone mentioned that already - if GAW introduced some kind of hold on external deposits, giving priority to HP conversions. But that would screw all those HT pumpers buying up "cheap" coins on coin-swap now.
No, what I'm saying is why spend money on exchanges to buy coins? They have enough debits to worry about with the HP->XPY->BTC/USD sell off from their own customers. They need to have the money to support this sell-off from their customers. And by doing so within paybase, they get the same effect from the exchanges that they want without having to buy coins from the exchanges. They can't control the price on the exchange, but they can manipulate behavior a bit by only guaranteeing the $20 via paybase.