Runescape's economy functions after demand and supply, right.
Obviously, with botters, there was a too large supply, causing prices to drop. However, now without bots,
supply is even bigger, because theres no more bots to process materials
Take mining for example; before, botters would smith. They needed to buy the materials.
Now, there's an overflow of materials, causing prices to drop even more dramatically on many resources.
Nobody wants to buy meterials though, because they're expected to raise in price.