There has been a growing need of cheese with no rise avalibility. Plain pizza's have skyrocketed in price but cheese, which you need to make plain pizza, has not risen because Jagex has put a cap on it at 108. sadly it doesn't even sell at this price. There is near to no movement in the Grand Exchange.
The following is theoretical discussion:
F2P'ers can only get it at respawns. while members can make it but don't because it isn't valuble enough for any to care. I suspect that some members are paying noobs to stand around and gather at the respawn points and buying it from them at over the g.e. max via personal trade. But to access this theoretical system would be difficult to gain access to.