Because the person who wrote that is attributing the transaction money to "money being put in". Transaction volume indicates how much worth of transactions are occurring not how much is being injected. Just the same way market cap can jump 1million dollars when 20k dollars was injected into it.
If you think that the price can rise in a sustained manner (more than a day or 2) on very large volume without new buyers entering the market, I don't know what to tell you.
Yes, the traders are buying at 17 and selling at 19, rinse and repeat. That does account for a good portion of the volume. But there have to be people actually buying at 19 in order for that to happen. Traders would be treading water and gaining nothing by buying from themselves at 17 and selling to themselves at 19. The people buying at 19 (and allowing the traders to cash out) are the ones bringing new money in.
If no new money is entering, then all the traders are just trading among themselves, and DRK and BTC are being redistributed among them, but no overall price movement should occur.
I never claimed that the entirety of the volume corresponds directly to the amount of money being put in. Just that the volume combined with the price increase indicates that SOME new money is being put in.