A doorbuster is a genuine price on a deliberately limited quantity, and both halves of that sentence matter. The offer is designed to move people rather than to move volume.
The allocation is fixed before the ad runs
Retailers commit to doorbuster quantities weeks ahead, ordering a specific number of units at a negotiated cost. That number is set by the promotional budget, not by expected demand.
Because the allocation is fixed, the offer sells out on schedule. Running short is the intended outcome rather than a failure of forecasting.
The published limit language exists to make that arithmetic legally visible, which is why quantity disclaimers appear in even the loudest advertisements.
Specifications are built for the price
Manufacturers often produce a specific configuration for promotional pricing, with a slower processor, less storage or a simpler display than the mainstream version of the same family.
The model number differs slightly, and the differences are real but easy to overlook. A buyer comparing names rather than specifications sees a bargain that is partly an illusion.
None of this makes the device bad. It makes the comparison against the standard model inaccurate, which is the effect the pricing depends on.
The loss is recovered elsewhere in the basket
A retailer may sell a doorbuster at little or no margin, accepting that outcome because the shopper drawn in rarely buys only the advertised item.
Cables, cases, warranties and storage carry far healthier margins, and they are placed within reach of the discounted product for exactly that reason.
The economics work at the basket level. A shopper who buys the doorbuster alone and leaves is the customer the promotion did not capture.
Timing changes what is available
Online doorbusters typically go live at a scheduled moment, and inventory is decremented as orders are confirmed rather than as items enter a cart.
This produces the familiar experience of a cart that empties at checkout. The system is behaving correctly; the allocation simply ran out during the transaction.
Stores handling the same promotion in person face the queue equivalent, where position in line does the same work that server timing does online.
Reading the offer before committing
The useful check is whether the discounted configuration matches what you would otherwise have bought at full price. If it does, the saving is straightforward and real.
If the specification has been trimmed to reach the headline number, the comparison to make is against similar machines at similar prices, not against the flagship model.
That single substitution turns a doorbuster from an emotional decision into an ordinary one, which is the state in which shoppers make better choices.