Who's selling? Well, imagine you wanted to sell your $300k ('market value') house on the market, as you needed liquidity. But the government says its price is capped at $25k. They enforce this by only letting notaries sign off on sales at that price.

Ownership of a house by law is only valid once a notary (government worker) signs off on the exchange of the deed, so nobody will buy the house without the notary's signature, as then they'd pay but not officially receive ownership. The seller who has the money, can now call the police and kick the buyer out of the house, as the buyer can't prove he owns the house as he never received the deed from a notary. So to sell, you must use a notary service, and through the notary, $25k is exchanged hands.

Now obviously nobody will sell $300k value at $25k, and obviously there are lots of home owners who at any point in time want liquidity and want to sell the house for whatever reason.

The most sensible thing to me is 1) not many are selling, even if 1 out of a million shares exchanges hands, whatever was the last price is the new price. So the 10% gain can happen with insignificant volume. And 2) some people are selling for $25k, while receiving $275k under the table through a different deal. It'd be discounted as you'd likely need to launder the money which has costs, but if the market price and the artificial price are far enough apart, people will do it.