Flash sales are built around urgency and scarcity as deliberate psychological tools, not just a byproduct of limited stock - understanding the mechanism helps separate genuine deals from manufactured pressure.
A visible countdown timer measurably increases purchase rates even when the underlying deal isn't actually better than a regular sale - the timer itself is often doing more psychological work than the discount.
A "only 3 left" message can reflect genuine low stock, or it can be a generic urgency tactic applied regardless of actual inventory - there's rarely a way to verify which, so it's worth not treating it as a hard deadline for a decision.
Retailers frequently plan flash sale inventory and pricing well ahead of time, meaning the deepest real discounts are usually on items chosen deliberately to draw traffic - not necessarily the items you were hoping to see discounted.