Dynamic pricing can have practical uses such as controlling traffic flow e.g. Atlanta highway toll roads, price change by speed of travel. For Singapore it is by a bloc basis. Airlines use this for yield management.

The practice of showrooming is giving competition to physical stores, when customers compare prices on their mobile phones right there in the store.
Shops match this by promoting a ‘price guarantee’ to match any online price that is lower.
For some ‘freemium’ models, e.g. music, the reference (basic) price for entry is zero.