Every $1 of bitAssets created are the equivalent of buying $3 worth of shares of the company called BTS by itself. While this is not really a profit profit, but the effect on the market cap should be the same as stock-buyback for that amount.
Not really though, because you are assuming someone uses fiat to purchase $3X worth of BTS to short the BitAsset into existence (or rather the short seller purchases $2X worth of BTS with fiat to provide the margin for the short and the BitAsset holder purchases $X worth of BTS with fiat to trade for the BitAsset they want).
The BitAsset holder could trade $X of USD for $X of BTS to later trade the BTS on the decentralized exchange for $X of BitUSD shorted into existence at the price feed (or just go from fiat to BitUSD directly and let arbitrage take care of the rest), and this would result in $X worth of buy pressure on the price of BTS (not $3X) assuming there was latent short demand at the price feed. In this case the BitUSD buyers are not really changing their exposure to the US dollar, just converting it into a cryptocurrency version of it.
On the other side of the coin, the above assumption implies that the short seller needs to purchase $2X worth of BTS using fiat to short sell, but this would increase their exposure to BTS. They wouldn't do this unless their position on BTS changed (they become more bullish). Assuming the market participants views on BTS has not changed, the only reason I can see for why new shorts would be created is because of the short sellers who had been waiting to short at the price feed but had not been able to since there was not enough BitAsset buy demand at the price feed. These bulls were already holding BTS and not selling it, so whether they keep it in their wallet, in cold storage, in an open order, or locked as collateral in a short position, it shouldn't have an effect on the price of BTS.
My conclusion from this analysis (and the one in a little more detail
here) is that for the price of BTS to go up (assuming the market participants' views haven't changed), there needs to be increasing outside demand for BitAssets purchased with fiat AND latent short demand limited by the price feed. Obviously, increasing buy pressure for BTS purchased with fiat in outside exchange as well as increasing buy pressure for BTS purchased with existing BitAssets in the decentralized exchange would also cause an increase in the price of BTS (the former directly, and the latter indirectly via arbitrage), but both of those cases require some market participants' views to change for them to want increased exposure to BTS. Furthermore, after taking arbitrage into account, it doesn't matter whether BitAssets or BTS are purchased with fiat in the outside exchange; $X worth of buy pressure for BTS or BitAssets in outside exchanges leads to $X worth of upward price pressure on BTS (not $2X or $3X, and it doesn't really depend on the collateral ratio requirement).