Why the Secret Spell Scroll system would have never worked.

I'm not sure it's fixable, even if they were to take out 90% of the mesos in the economy so that in theory mesos was worth 10 times what it previously was, would it just go back the same way?

Then they could just purge again. Maintaining an economy is not something that can be done once and be done with it, it is, or rather should be, an ever going process.