PSA: The value of upgrading all of the rupie mines from level 30 to 40 has gotta be one of the most horrendous values I've ever seen and should be reserved only for completionists since the benefit of doing it is so comically small.
Actually, scratch that.
Even hardcore completionists should resist the urge to splurge since it would be the most wasteful usage of orbs ever
which won't stop me from doing it.
Cost to upgrade all four rupie mines from level 30 to 40:
204,000 rupies
6,000 T1 light orbs
1,660 T2 light orbs
652 T3 light orbs
388 T4 light orbs
All of
that will get you...
*drumroll*
...
7,227,000 extra rupies over the span of...