diff --git a/packages/api/src/routes/procurement.ts b/packages/api/src/routes/procurement.ts
index bc02418..80f4dfe 100644
--- a/packages/api/src/routes/procurement.ts
+++ b/packages/api/src/routes/procurement.ts
@@ -819,6 +819,24 @@ procurementRouter.get("/availability", async (_req: Request, res: Response) => {
         ) s ON true
         WHERE t.speed_gbps IN (100,200,400,800,1600)
         GROUP BY t.speed_gbps
+      ),
+      pm AS (
+        -- per-SKU paired price momentum (30d vs prior 30d), bias-free: only SKUs in
+        -- both windows; aggregate the median per-SKU pct delta per speed tier.
+        SELECT speed_gbps,
+          ROUND(PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY (med_now - med_prior) / NULLIF(med_prior,0) * 100)::numeric, 1) AS price_delta_pct
+        FROM (
+          SELECT t.speed_gbps, t.id,
+            PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY po.price) FILTER (WHERE po.time >= NOW() - INTERVAL '30 days') AS med_now,
+            PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY po.price) FILTER (WHERE po.time >= NOW() - INTERVAL '60 days' AND po.time < NOW() - INTERVAL '30 days') AS med_prior,
+            COUNT(*) FILTER (WHERE po.time >= NOW() - INTERVAL '30 days') AS n_now,
+            COUNT(*) FILTER (WHERE po.time >= NOW() - INTERVAL '60 days' AND po.time < NOW() - INTERVAL '30 days') AS n_prior
+          FROM price_observations po JOIN transceivers t ON t.id = po.transceiver_id
+          WHERE t.speed_gbps IN (100,200,400,800,1600) AND po.price > 0 AND COALESCE(po.is_anomalous,false) = false
+          GROUP BY t.speed_gbps, t.id
+        ) per
+        WHERE med_now IS NOT NULL AND med_prior IS NOT NULL AND med_prior > 0 AND n_now >= 2 AND n_prior >= 2
+        GROUP BY speed_gbps
       )
       SELECT
         sk.speed_gbps,
@@ -828,14 +846,16 @@ procurementRouter.get("/availability", async (_req: Request, res: Response) => {
         COALESCE(st.skus_in_stock,0)::int    AS skus_in_stock,
         COALESCE(st.skus_with_stock,0)::int  AS skus_with_stock,
         CASE WHEN COALESCE(st.skus_with_stock,0) > 0
-          THEN ROUND(100.0 * st.skus_in_stock / st.skus_with_stock)::int ELSE NULL END AS in_stock_pct
+          THEN ROUND(100.0 * st.skus_in_stock / st.skus_with_stock)::int ELSE NULL END AS in_stock_pct,
+        pm.price_delta_pct
       FROM sk
       LEFT JOIN sup ON sup.speed_gbps = sk.speed_gbps
       LEFT JOIN st  ON st.speed_gbps  = sk.speed_gbps
+      LEFT JOIN pm  ON pm.speed_gbps  = sk.speed_gbps
       ORDER BY sk.speed_gbps DESC
     `);
 
-    type Row = { speed_gbps: string; sku_count: number; suppliers: number; suppliers_prior: number; skus_in_stock: number; skus_with_stock: number; in_stock_pct: number | null };
+    type Row = { speed_gbps: string; sku_count: number; suppliers: number; suppliers_prior: number; skus_in_stock: number; skus_with_stock: number; in_stock_pct: number | null; price_delta_pct: string | null };
     const tiers = (result.rows as Row[]).map((r) => {
       const sup = r.suppliers ?? 0;
       const inStockPct = r.in_stock_pct ?? null;
@@ -849,17 +869,33 @@ procurementRouter.get("/availability", async (_req: Request, res: Response) => {
       const trend = r.suppliers_prior > 0
         ? (sup < r.suppliers_prior ? "tightening" : sup > r.suppliers_prior ? "loosening" : "stable")
         : "stable";
+      const priceDelta = r.price_delta_pct != null ? parseFloat(r.price_delta_pct) : null;
+      const priceTrend = priceDelta === null ? "unknown" : priceDelta > 3 ? "rising" : priceDelta < -3 ? "falling" : "stable";
       const drivers: string[] = [`${sup} active suppliers`];
+      if (trend === "tightening") drivers.push(`supplier base shrank ${r.suppliers_prior}→${sup} vs prior 45d`);
+      else if (trend === "loosening") drivers.push(`supplier base grew ${r.suppliers_prior}→${sup} vs prior 45d`);
       if (inStockPct !== null) drivers.push(`${inStockPct}% of tracked SKUs in stock`);
-      drivers.push(`${r.sku_count} SKUs`);
-      if (trend === "tightening") drivers.push(`supplier base shrinking (${r.suppliers_prior}→${sup})`);
+      if (priceDelta !== null) drivers.push(`price ${priceDelta >= 0 ? "+" : ""}${priceDelta}% (30d, same-SKU median)`);
+      drivers.push(`${r.sku_count} SKUs catalogued`);
+      // Plain-language WHY, built only from real per-speed signals
+      const reasons: string[] = [];
+      if (availability === "scarce") reasons.push(sup <= 3 ? `only ${sup} supplier(s) offer it` : `near-zero stock coverage`);
+      else if (availability === "constrained") reasons.push(`limited supplier base (${sup})`);
+      if (trend === "tightening") reasons.push(`supplier base is shrinking`);
+      if (priceTrend === "rising") reasons.push(`prices rising ${priceDelta}% on the same parts`);
+      if (priceTrend === "falling") reasons.push(`prices easing ${priceDelta}%`);
+      if (inStockPct !== null && inStockPct < 50) reasons.push(`${inStockPct}% in-stock coverage`);
+      const why = reasons.length ? reasons.join("; ") : `broad supply: ${sup} suppliers, ${inStockPct ?? "n/a"}% in stock, stable pricing`;
       return {
         speed_gbps: parseFloat(r.speed_gbps),
         sku_count: r.sku_count,
         suppliers: sup,
         in_stock_pct: inStockPct,
+        price_delta_pct: priceDelta,
+        price_trend: priceTrend,
         availability,
         trend,
+        why,
         drivers,
       };
     });