I know how to solve (chinese) farmer hackers and mastery book issues

That's one example that I'm familiar with. I highly doubt Shadow Shifter 20 is the only expensive book. This could have a bigger effect of basically deciding what class you play based on how many mesos you have.

That's why things would have to be balanced, rather than strictly based on prices in the free market. Some things are impossible to find, so they're billions, when they're skills like "Dark Spirit Up" (The weapon attack increasing Beholder passive) that shouldn't even be higher than 100m.