Mining Rig

Strategy and Synergy
Each area has 7 zones, for a 21 sera profit per zone. The shopkeeper sells it for 90 sera and appears near the end of each zone. Therefore, it is never a good idea to purchase the Mining Rig past zone 4, as it will only limit the player's options instead of paying for itself.

Trivia
A "mining rig" is a term for a computer used to passively generate bitcoin.