Sorry for replying late. But here we go.
Back then before the G.E came... no one ever mentioned people buying out items. Its virtually impossible. Your gonna have to go to each world and buy the items you want. To buy out an item you need a grand exchange or a huge group of players going around worlds buying items out. But it never happened. Ive been playing since 04, and never heard of people buying out items. Plus everyone has there own price for that item.
The bots did keep items in check. Despite how many auto fishers there were, lobsters did not go below 250 gp, or over 300gp each. Same with Sharks, Strength Potions, Yews especially and flax. Yews were around 300 each and made the yew longbow have a value so people alched it. Same with alot of prices.
As for essence read here:
http://www.moparisthebest.com/index.php/2006/04/
Your last paragraph is just proof that Jagex can not tackle Autoers, and had to remove the best two things of the game to do some damage. Its there game, there choice. Eventually alot of players will really get bored and quit, and the amount of players playing will be so low Jagex will revert some updates. Mark my words.