I am a student and want to buy a silver ring for my girlfriend, but what if he thinks it is too cheap?

First of all, you can think about what she likes at ordinary times, and then meet her general requirements according to the situation

Secondly, some girls are just joking, which requires you to analyze it according to the context.

Then, you can tell her that this is just what she occupies in the wedding ring, and you don't have to tell her the price (of course it depends on your relationship)

Anyway, the most taboo is to raise the price, in case the woman is found angry.