There is no SBD entering the system right now from posts. It was suspended by the blockchain due to there being too much of it. There is some entering though SPS funding, but that stays in the SPS treasury until there are approved proposals. Right now there are a few approved proposals but not that much approved spending overall; most of the SPS funding SBD just stays in the treasury (and off the market).
The @sbdpotato posts are doing exactly what you suggest: buying what is already on the market.
With only 65k steem you can buy the supply on Bittrex and bring the price to 1 USD.
Such big market buys don't more the price on a sustained basis. They create price spike and then it goes back down.
It wasn't suspended because there is "too much". That is not how the economic model work. It's about the debt ratio, Wich is related to value, not volume.
And this "experiment" is failed from the beginning, because you people are trying to beat the market laws.
You can manipulate it briefly, but eventually it will self correct.
The moment the price start rising, people will start to sell sbd, to reduce losses.
The moment the price go up to the point where the debt ratio is less than 10% and sbd is printed again, people will again dump it on the market.
How can't you people see there is only one solution to this: make sbd an attractive asset to spend/hold.
Still, this is trying to solve a non-existent problem, while the front-page of the platform look unnatractive.