I bought a new bicycle, _____ was very high.

逗号后面是一个定语从句。定语从句要表达价格，自行车和价格之间，需要用介词 of 表示“所属关系”，因此就有了：the price of which；还可以用 whose price 表示。

1. I bought a new bicycle, the price of which was very high.

2. I bought a new bicycle, whose price was very high.