This research aims to assess the effectiveness of using the book value and market value frameworks to estimate the implied required rate of return (Ke), examining their subsequent impact on determining the fair value of common stocks and comparing their effects. Traditional valuation models, primarily based on the Capital Asset Pricing Model (CAPM) and market-based metrics, often suffer from increased volatility and conflicting prices in public stock markets. This distorted environment negatively impacts the reliability of cost of equity estimates. To address this vulnerability, this research shifts its analytical focus to a data-driven framework for a group of 10 Iraqi industrial companies over the period 2015-2024. This framework applies the best solutions and models to support the implied rate of return (RM), specifically using the return on investment (ROI) of the companies in the research sample and comparing it to the same implied ROI using earnings per share (EPS) for the same companies over the same period (book value and earnings). The goal is to determine the best approach for estimating the required rate of return and its role in the fair value of the stock, while also controlling for the degree of systematic risk, company size, and earnings quality to understand the direct impact of the two models. Their impact on the accuracy and comparability of fair value. Through periods of macroeconomic distress or systemic market shocks, the first model framework provides a more stable and reversible required rate of return compared to the second model. Consequently, derived fair values exhibit a tighter convergence with long-term intrinsic values, effectively reducing valuation errors resulting from market movement. The analysis highlights a critical gap in the valuation literature by demonstrating that accounting metrics are not merely retrospective reporting requirements, but rather structural anchors capable of stabilizing equity valuations. Its most important findings have profound implications for institutional investors, financial analysts, and regulatory bodies seeking robust valuation methodologies less susceptible to anomalies in temporary market movements.