When sourcing Spanish Mackerel, the price is primarily driven by freshness grade, freezing method, and size specifications. Buyers should look for 'Sea-frozen' (BQF - Board Quick Frozen) products which command a premium over 'Land-frozen' due to better texture preservation. Key quality markers include clear, bulging eyes, firm flesh elasticity, and intact skin with vibrant silver-blue luster. Prices will fluctuate based on weight categories, typically graded as 200-300g, 300-500g, or 500g+ per piece.