Critique a personalized pricing proposal

A growth lead proposes: "Train a model on app features (device model, zip code, time of day, past purchases) to predict each user's willingness to pay, then show every user a different price for the same product, up to 25 percent apart. In a back-of-envelope estimate this raises revenue 8 percent."

Write your critique. Cover the economics, the measurement problem, fairness and legal exposure, user trust, and what you would propose instead. What would you need to see to approve a limited version?