With the Invisibility Technique, there was a way out, and with a way out, one could boldly make money, and successfully making money meant paying off debts and rising to the status of a true top spender in alchemy. Even if he failed, there was no loss, as the loan-purchased Magic Mirror could be transferred. After all, it could be used again simply by re-binding it, and it would even inherit the remaining repayment installments.
Many Hell Demoons harbored thoughts of killing and looting, for if they killed an owner of a Magic Mirror, they could then obtain this "civilian Divine Artifact" without spending any money.
But this approach was not without risk, after all, a Demon that had to steal a Magic Mirror wasn't very powerful, and those capable of using a Magic Mirror were essentially carrying a high-level Mage with them at all times, who could even loan out magic spells in critical moments, albeit at a high interest.