A price comparison provided by a retailer. For example, regular price $100, sale price $80. External reference prices are generally used to increase consumers’ perceptions of price savings. Abbreviated ERP. Technically, any price displayed by a retailer is an ERP, even in the absence of direct price comparisons. Consumers use ERPs to update their internal reference price for a given marketplace offering. ERPs which seem too high or too low, or are rooted in special circumstances (going out of business sales) probably have little effect on consumers’ future price expectations.