Xianyu is originally a seafood market.

Whether you can find good deals depends not only on luck but also on your searching skills.
The same item, some people search for half a day and only find high-priced options, while others change a keyword and immediately find cheap and suitable ones.
To put it simply, Xianyu isn't lacking good products; many people just don't know how to find them.
What you search for basically determines what you can see.