With unstable supply/demand ratios, prices are quick to rise and slow to fall.

Prices can go up very easily as vendors charge more due to real or perceived scarcity and others raise their prices to match because they want to increase their profits.

Prices only go down when one company tries to undercut its competitors, though. And, of course, they only undercut their competitor's price by a little, because they still want to make as much profits as possible. This will hopefully result in a back-and-forth competition of trying to undercut one another and steal market share from the other by offering a lower (but still profitable) price. But unless the market is extremely volatile and liquid, this back-and-forth takes time, leaving consumers to wait while the next company contemplates its next price cut.

And that's the optimistic scenario, assuming there's no oligopoly and no price collusion. If either of those are in play (and they often are), then prices will only go down if a new competitor enters the market.