Excluding textbooks for classes, I bought this for ~$300 (several several years ago as a special treat)
Most of my collection is thrifted/bought from garage sales (for a quarter to a dollar usually) but I do have a handful of nicer ones.
It’s a set of commentaries on The Book of Documents/尚书, an ancient compilation of the histories of early Chinese dynasties. That text is very laconic and low on detail, but this book adds a lot of interesting stories in its “interpretation” of what Confucius (supposedly) wrote.
I have an interest in historiography, especially Chinese, and relatively few ancient Chinese texts are available in English translation (especially if you give a shit about accuracy, don’t get me started on the I-Ching…)