What is the price of a monetary union, or of leaving one, for that matter? These questions are now being raised by the eurosceptic parties that are gathering momentum in Germany, the Netherlands and Finland, all considered to be 'core' eurozone countries.

United by their grievance over the cost of the bailout to the crisis eurozone countries, these parties advocate a future in a drastically different European Union.

Student or retired? Then this plan is for you.

But as their parties' popularity rises, so do questions about the practical implementation of their ambitions.

In the Netherlands Geert Wilders and his Party for Freedom – currently polling at around 20 percent – advocate a Dutch exit from both the euro and the EU.

In February this year, Wilders announced he had a report providing rationale for this position. The document, put together by research company Capital Economics, assessed the impact of The Netherlands leaving the EU – a so-called Nexit.

"Overall, the various strands of analysis point to Nexit being a long-term benefit to the Dutch economy and, more than likely, a short-term help in easing the Netherlands out of its current economic ills," the report said.

Finns party lofts Greek and Cypriot exit

Similar cost benefit rhetoric has also been adopted by the Finns party (polling at 15-20 percent).

"For us this is an economic question, we are committed to the interests of Finland. If the euro is in the interests of Finland, I will happily applaud it – but so far nothing has indicated this is the case," says Finns MEP Sampo Terho.

Speaking on the behalf of his party, Terho demands that the real costs and benefits of the EMU for Finland are calculated. The party is a long-standing critic of the bailouts to Greece and other crisis countries.

"Separating some of the current crisis countries from the EMU would in their mind stop the transfer payments between the member countries and remove the moral hazard of the monetary union," says Lauri Holappa, researcher at the Department of Political and Economic Studies at the Universtiy of Helsinki.

But can a monetary union work without transfer payments?

Sixten Korkman, professor of economics at Aalto University, says no. He also dismisses the possibility of an internal market with similar mechanisms.

"The Finns don't understand or don't accept the fact that our co-dependence demands significant co-operation to keep different problems in check. A functioning internal market cannot be guaranteed through a loose free-trade union, supranational use of power is also necessary."

Sampo Terho, for his part, says Finns understand this reality, but don't accept it.

Just do the maths?

Calculations of any exit scenarios are complex and biased assumptions are hard to avoid in any predictive models.

This is why Sylvester Eijffinger, professor of financial economics and European financial and monetary integration at the University of Tilburg, is not convinced by the report presented by the Dutch Freedom party.

"The analysis of Capital Economics is very biased towards high costs and low benefits of the EU and takes a very optimistic view on exiting by the Netherlands which has no empirical basis," Eijffinger said in an e-mail interview.

"It is very difficult to calculate exactly the costs and benefits of exiting the EU but is clear that being outside the EU will not be beneficial for the Netherlands as a small and open economy," said Eijffinger.

He added that he has never seen "any exit strategy for any member state of the EU that is promising in terms of economic outlook".

Germany is key

So far the Wilders report has not influenced eurosceptics in other member states.

The Finns' Terho says he has never heard of it and in Germany, the euro-exit debate has faded after a brief hype in 2013 following the unexpected success of a party centred around the issue.

Alternative fuer Deutschland (AfD) was formed in March 2013 – six months before general elections – challenging the political establishment on its view that there is "no alternative" to the euro.

Its core message at the time was a breakup of the eurozone and the return to the Deutsche Mark.

The AfD did better than expected, gathering votes from the losing Liberals and disenchanted supporters of centre-right Chancellor Angela Merkel. But it missed the five percent threshold to enter the Bundestag with a small margin.

For the EU elections on 25 May, however, there is no threshold and the AfD is expected to win six to seven seats in the European Parliament. Polls published early May put AfD at six and seven percent, respectively.

Its main campaign topic is no longer the euro-exit, but rather immigration, curbing the Brussels bureaucracy and a repatriation of powers from EU level.

"This is because the euro is not such a big topic any more in German public opinion," says Michael Wohlgemuth, the head of the think tank Open Europe Berlin.

The euro is indeed still popular in all the core countries with 71 percent of the population supporting it in Germany and the Netherlands, and 75 percent in Finland, according to the latest Eurobarometer study from 2013.

This means that advocating a eurozone exit goes contrary to the majority of popular opinion.

In its manifesto, the AfD says it would prefer a "dissolution" of the eurozone, but if that doesn't work, then at least a change to the EU treaties so that countries can exit the eurozone.

Currently there is only a provision for leaving the EU as a whole, but not for leaving the euro.

Another option floated in the AfD manifesto is for the "stability-oriented" eurozone countries – meaning Finland, Germany and the Netherlands – to form their own monetary system.

This is the pet idea of Hans-Olaf Henkel, the former head of the Federation of German Industries and a prominent figure in the AfD.

But this plan is problematic, says Carsten Brzeski, chief economist with ING Bank which in 2011 carried out a study calculating that the breakup of the eurozone would exceed the cost of rescuing it.

"If a country exits the euro on its own, let's say Greece, and returns to the drachma, it would have to change all its assets from euro. There would be a bank run, capital restrictions – it still sounds very bad even if they can devaluate their currency," he says.

"And if the northern countries were to start a smaller eurozone, their currency would appreciate and their exports would go down the drain, bond yields would remain very low or fall even further, which would lead to financial bubbles to a much larger scale than what is happening now in Germany," Brzeski adds.

The last resort for AfD would be for Germany to leave the euro on its own and return to the Deutsche Mark.

The AfD, which likes to refer to itself as a party of "economy professors", has developed a whole theory of how an exiting country could introduce a parallel currency for a transition period and how the exchange rate would be established.

But critics say such ideas may make sense in an academic world, but that they would never work in practice.

"Take this idea of allowing countries to leave temporarily – like going to the gym and then coming back to the eurozone when they are fit. It's a nice idea, but it clearly opens the door to financial markets to speculate against them. Plus, the remaining eurozone would need to increase its firefighting capacity to shield the whole thing," Brzeski says.

"Some of the ideas are not wrong, but the practicality and spillover effects are very chaotic and difficult to foresee," he adds.

At the moment the euro-exit question is on the backburner as the eurozone has moved out of crisis mode.

However, key countries in the single currency areas still have severe problems. If the eurozone was ever called upon to bail out a large country, the questions raised by anti-euro parties would once again come to the fore.

Mikael Brunila reported from Finland, Valentina Pop reported from Germany and Peter Teffer reported from the Netherlands