I searched and didn't see this issue.
Running:
cBukkit 1.1 R3
P.Stones 8.0.1
Vault 1.2.6
Essentials core/chat (no other extras)

This isn't a very serious issue, because the mechanics work. The user will place a block we've set at a price, they will get charged the amount, the stone will be placed and work fully, but they will get an error "You have insufficient funds."
Beyond the rogue error, it works entirely.

I remember fixing this, dunno if i released the fix. Let me know here if it happens on next release. Ill close the ticket for now.