different to the digging process, you make nothing like a progress in farming arc chest. you might get nothing even if you farm days after days.
best thing to do now probably is to buy cheap from lucky one timer, and top up the price.

imo, the game has become too serious that you need to think how to do good business, not recommended for people who is looking for holiday/time off from real life. and it is worsened by many talk about "maintaining rarity" and "effort"