Serious price discrimination emerges with the development of big data and mobile networks, which harms the interests of consumers. To solve this problem, we propose a blockchain-based price consensus protocol to solve the malicious price discrimination faced by consumers. We give a mathematical definition of price discrimination, which requires the system to satisfy consistency and timeliness. The distributed blockchain can make the different pricing of merchants transparent to consumers, thus satisfying the consistency. The aging window mechanism of our protocol ensures that there is no disagreement between any node on the consensus on price or price discrimination within a fixed period, which meets the timeliness. Moreover, we evaluate its performance through a prototype implementation and experiments with up to 100 user nodes. Experimental results show that our protocol achieves all the expected goals like price transparency, consistency, and timeliness, and it additionally guarantees the consensus of the optimal price with a high probability.