Because 316 stainless steel is more expensive than 304 stainless steel in terms of the materials used to make it and the cost.
First of all, the first thing to say is the food grade issue. In life, people often encounter the purchase of stainless steel items, namely 304 is not food grade, in terms of materials, stainless steel 304 does reach the food grade. There are three common food grade types on the market, namely 304, 316 and 430 stainless steel. 304 is usually small household appliances or mugs, 316 is used in medical equipment and 430 is stainless steel used as knives. But one thing worth keeping in mind is that the term food-grade does not only mean that the material has been made to a food-grade standard, but also the standard of its manufacturing process.
The second issue is that of corrosion resistance. For different stainless steel materials, their corrosion resistance must be somewhat different. Otherwise, 304 can only be used for everyday household appliances, yet 316 can be used for medical equipment. But the corrosion resistance of 316 or 304 stainless steel is not very different between them, but 316 stainless steel material has a very high content of chloride ions, then 316 stainless steel will be slightly better than 304 stainless steel, more suitable. This is why 316 stainless steel is chosen as the reason for medical equipment.
Currently, we can't tell the difference between 304 and 316 stainless steel with the naked eye, so many companies usually sell 304 stainless steel cutlery as 316 stainless steel to increase profits. Even though it's just a different number, they more than double in price, and many people say that when they purchased their own flatware, they went into the pit many times because they didn't understand the difference between them, and many times we paid the price of 316 stainless steel for 304 stainless steel flatware, which amounted to twice the amount of money.
We can distinguish between these two types of stainless steel by looking at the grade, and secondly, we can also use the stainless steel potion to distinguish between the stainless steel, a drop of potion on the stainless steel, naturally, you can see the difference between 304 and 316. However, this method is impractical, because we usually can not just bring out the potion, and the potion has a corrosive effect on the stainless steel, which is impractical for distinguishing cutlery. It is recommended to use a magnet to distinguish between the two types of stainless steel, in which 304 can not be attracted by a magnet, so it is easy to distinguish, but if you use this case to distinguish, the precision will be a little low, and the credibility will not be very high.