Shandong Fiberglass (605006): Estimated Cost Basis of Dominant Trading Capital: Cost-Basis Assessment of Dominant Market Trading Activity

The cost basis of dominant trading capital is an important variable for assessing market repricing, potential support levels, and supply pressure; however, public market data cannot directly identify the true account-level cost basis of individual participants, creating a fundamental identification gap in market-microstructure research. Using Shandong Fiberglass (605006) as the research setting, this study uses public shareholder and share-repurchase disclosures, together with anchored volume-weighted average price (AVWAP), as the primary identification framework, supplemented by a turnover-survival model, cost-basis density analysis, and large-lot fund-flow data for cross-validation. The results indicate that the most defensible core cost-basis range for currently active dominant trading capital is approximately RMB 14.70–15.20 per share, with a central estimate of about RMB 14.95–15.00. The RMB 14.50–16.00 range is the most prominent repricing and turnover zone, while RMB 15.50–16.00 also shows features of high-cost inventory and concentrated supply pressure. As recent high-turnover trading has increasingly accumulated at higher price levels, the explanatory weight of the earlier RMB 12.00–12.50 low-price inventory for the current cost center has declined, whereas RMB 13.00–14.30 remains an important secondary low-cost inventory layer. By distinguishing directly disclosed cost anchors, historical trading zones, and current market-based cost proxies, this study develops a reproducible, updateable public-data framework with explicit invalidation conditions, providing a methodological basis for equity cost-structure analysis, market-microstructure research, and trading-risk management.