It depends on the price of your mine.
We are 25g.
The gems in our area are very valuable now, more than 60 g.
It's also 20g cheaper.
Gemstones can now be combined into a sapphire one day, which means that they can give you 20-60g a day.
I don't think gems are a skill to make money.
The main benefit is the jewelry on the top of this group.
At present, the occupations that make money are double mining, stroking and engineering.
Everything else is just so-so