It may be that the root is inflamed and stimulates a big nerve. If it is inflammation, root canal treatment is needed, and the cost depends on the specific unit charge, because the hospital charges no need to buy or sell products in the market, and the treatment agreed by different units may be different.

As for the removed crown, whether it can be used again depends on the crown itself and the condition when it is removed. I suggest you find a professional institution for diagnosis and treatment consultation!