WIESBADEN, Germany (MarketWatch) — Gold bugs will be glad to know that the spa-town kaffeehaus in which I’m now sitting will not accept my Visa card as payment for the Sonntag spezial.

That’s because the reluctance of German merchants to pay U.S. banks’ credit-card fees is just one of many reasons the euro won’t survive.

Simply put, you can’t force a single currency on a continent where people as frugal as Germans coexist with Spanish, Italians, Greeks and Portuguese.

And the future demise of the euro will be the type of event that makes those who question the integrity of all paper currency jump for joy.

The multinational nature of the euro is a situation 2,000 years in the making, but the biggest immediate problem for the currency is that those trying to save it have no credibility.

To be sure, the rising yields on Italian and Spanish bonds reversed course after the European Central Bank issued an emergency statement saying it would begin buying those countries’ debt.

“ The future demise of the euro will be the type of event that makes those who question the integrity of all paper currency jump for joy. ”

Unfortunately, the statement also indicated that recent measures announced by those countries will “strengthen fiscal discipline and underpin the recovery in economic activity and job creation.” Is there anyone who really believes that either Italy or Spain is about to have a burst of economic activity or job creation big enough to boost revenue? And who believes Silvio Berlusconi’s pledge that Italy will balance its budget in 2013, a year earlier than planned, given that Italy hasn’t accomplished that feat in a decade?

For a look at what happens to leaders who peddle such pabulum in the face of a wizened public, Berlusconi may want to take a look at former Egyptian leader Hosni Mubarak’s new jailhouse digs.

Perhaps the only ones who do believe in the current euro optimism are the bond buyers at the private banks who are being strong-armed by Europe’s political leaders into financing new euro-zone sovereign debt.

Those banks will be the same ones on the hook if (or when) either Italy or Spain default. It won’t be called a default, of course, because the ECB will guarantee a market for any new euro-zone government bonds with its new European Financial Stability Facility.

Meet QE’s European cousin — the EFSF

That’s the brand-new fund created so that European leaders could call the recent Greek default something other than what it was.

It was relatively easy to create, since the only thing needed to back it up was the ECB’s ability to print another €440 billion (that’s $628 billion in paper dollars).

Not since the Fed printed more than $1 trillion for QE1 and QE2 has a currency seen so much inflationary pressure created in so short a time.

But expanding that EFSF to cover much-larger defaults by Italy and Spain won’t be so easy, given that the head of the Bundesbank, Germany’s central bank, is on record opposing the new bond purchases that have just begun.

And here’s where we get to the sticky part for the euro, because no amount of worthless statements by Europe’s political or financial leaders can change this fact, which has been centuries in the making: Germans are way, way more frugal than their southern European counterparts.

German frugality will trump German patience

Perhaps “frugal” is too kind a word. With all due respect to a nation of 80 million hard-working people, it’s more accurate to call the Germans cheapskates.

German Chancellor Angela Merkel at a July news conference in Berlin after signing on to a second rescue package for Greece. Reuters

I was reminded of this by my German friend and schnitzel companion, a Wiesbaden resident who a day earlier insisted that we use a half-dozen free plastic produce bags to carry our cache of pilsner bottles back to her apartment, rather than shell out 15 euro cents for a paper sack that would have made the task much easier.

Germans don’t mind a little hard work in the name of good beer. When they do spend their money, it’s to travel to countries with nice beaches, places like Greece and Spain and Portugal, not to buy frivolous items like grocery bags.

The Germans are also patient, as demonstrated by the tax that residents of the former West Germany still pay every month to cover the costs of reunification with East Germany, an event that occurred nearly two decades ago.

Yet even patient Germans have their limit, something I was reminded of when I had to ask my dining companion to cover the cost of our meal, given that my plastic was verboten and, having arrived on a weekend, I’d yet to exchange any currency.

She paid it, but the look on her face as she did so made it clear that I’d be paying her back as soon as the banks opened in the morning.

I was good for the money, dutifully exchanging my ever-falling dollars for a currency that, in the eyes of gold bugs at least, will soon be only slightly less worthless.

But will the Spanish and Italians — or Greeks or Irish or Portuguese — be as diligent in repaying their debts as I was? Their fiscal track records, and the current global economic malaise, doesn’t inspire confidence that they will.

If (and when) they don’t, it will trigger a dynamic that will be the ultimate driver of the euro’s collapse.

Once a critical mass of Germans recognizes what euro membership is costing their country, once the inflation driven by the printing of those billions of new euros makes those cherished beach vacations — and everything else — that much harder to afford, the Germans are going to elect a government that will dump the euro.

It will be a financial disaster, of course, given that German banks hold more euro-denominated assets than anyone.

But it will happen, given that the only thing more durable than German patience is German frugality.