Is rubbing calligraphy really valuable? How much can I sell and where can I sell it?

The rubbings are valuable, but the engravings are not. Before the Song Dynasty, the Ming and Qing Dynasties were all ordinary. Because there are too many pagodas and Tang monuments, they cost about 20 thousand, not necessarily. This thing can't be bought with money. It's really sad. It is recommended to go to a regular place to buy and ask for an invoice. Beilin should be bought. Is it all true?