Another option is to use a seat roller or sander, a cheap tool that can re-flat the worn seat. Be careful not to use too much time or use too much force when using this tool, because the seat is made of soft metal, you can easily wear it too much.
When using the sander, first remove the faucet spool and insert the seat roller down into the seat in the faucet body. Rotate the tool a few times clockwise with moderate force. Then use a cloth to wipe off the metal scrap falling from the seat.