Firstly there are ASIC miners, which will not sell HUSH for anything less than their cost to mine it. HUSH is compatible with the same miners as ZEC, ZEN, KMD, ARRR and a few other coins, so very large farms have the potential to switch to the Hush network. Autoswitching software does this automatically for large miners.
Miners also have capital costs, the cost of the mining equipment. When they buy new equipment, they are more likely to sell and less likely to HODL, until they break even.
To send a HushChat is 0.0001 HUSH on average (about 500 characters of text) and so 1 HUSH "purchases" 10,000 encrypted messages (we call them memos) on Hush mainnet. Larger memos are possible (up to 200KB currently) and group chats are planned, which will use more Hush because they take up more block space and need to pay a higher fee to miners.
Traders usually store Hush on an exchange and don't use privacy features. They don't really drive the price or value so much as follow it.