As of my last update in September 2021, 316 stainless steel is generally more expensive than 304 stainless steel. The main reason for this price difference is the difference in their alloy composition.
Stainless steel grade 304 contains a higher percentage of chromium (18-20%) and nickel (8-10.5%) but has a lower molybdenum content (0.08% max). On the other hand, stainless steel grade 316 contains a higher percentage of chromium (16-18%), nickel (10-14%), and a significant amount of molybdenum (2-3%).
The presence of molybdenum in 316 stainless steel improves its corrosion resistance, especially in harsh environments with chloride exposure, making it more suitable for marine applications and industrial settings. However, the added molybdenum contributes to its higher cost compared to 304 stainless steel.