I don't think anyone have Hellium to sell. There was no ICO and bounty hunters are not paid as i know.
They said that everything will be after Hellium network launching but there are no news.
True, since it is not released. However, you could sell the wallet that you have that will eventually have HLM when it launches. If you had SPR at the time of the airdrop then you would have HLM in the same quantity and could sell that off.