fixed price; set price
Refers to a price that is predetermined and not subject to bargaining; often used in commercial contexts.
This store sells at fixed prices.
The fixed price is displayed, so you can buy with confidence.
定価 is the standard term for 'list price' or 'regular price', while 正札値段 is an older, more specific term for a fixed price that is not negotiable.
Compound of 正札 (しょうふだ, 'price tag' or 'fixed price') and 値段 (ねだん, 'price'). The exact historical derivation is uncertain, but it likely emerged in merchant contexts to emphasize non-negotiable pricing.