"It's Scotland's pound and we're keeping it," they say. We are still being treated like children who do not understand economics.
The pound is the currency of the union. It is not Scotland's pound, nor is it England's, Wales' or Northern Ireland's pound. Scotland proposes leaving the union. You cannot divorce and expect to retain the joint account. When you're single again you must establish your own account and pay your own way.
It's no good repeatedly telling your ex-partners that it's somehow in their interest to continue underwriting your debts; after the 2008 crisis they won't believe you.
If Scotland used the pound unilaterally we would have to accumulate pounds by trade, since our government could not create for itself an increased supply of a foreign currency. Failure to generate a trade surplus would thus preclude the blithely promised fairer society. You might want it, but you can't have it if you can't pay for it.
Without a central bank, borrowing would become more expensive, especially if the Scottish government followed through on its reckless threat to throw over responsibility for its share of the UK National Debt. Remember a Scottish Chancellor under a Scottish Prime Minister recently increased that debt to rescue The Royal Bank of Scotland. No-one lends cheaply to those perceived as defaulters.
Loss of financial sector jobs could easily run into tens of thousands, reducing tax revenues, increasing the Scottish government's need to borrow and raising interest rates still further.
Using sterling without agreement has costs. It's not just a matter of thumbing our noses at the rest of the UK and saying we'll do as we like.