The men, both aged 22, were barbecuing at a mountain forest home belonging to one of their grandfathers when the fire broke out on 30 December last year.
The huge bill for the two students was calculated by local officials based on a formula used to determine the extent of damage caused by the fire.One of the students told Italian media they were "scapegoats" for the blaze.
Speaking to Italy's La Stampa newspaper, one of the university students said he was "deeply sorry" - but said there were multiple sources of the outbreak.
"We are the scapegoats of a fire that cannot be explained," he said, adding: "We are the real victims of this story.
"[We] immediately alerted the fire brigade and threw ourselves at the flames to try and put them out."
Prosecutors, however, traced the path of the fire back to the property and said it had been started by embers from the barbecue, coupled with extremely dry conditions. The two young men were found jointly responsible, along with the owner of the property.
The fire lasted for several days, destroying some 1,000 hectares of forest on Monte Berlinghera - the damage caused to some 100 hectares was said to be irreversible.The fine of €13,542,000 was calculated by forest police based on an established formula under local laws.
La Stampa reports that the regulation calls for a fine of €118–€593 per square metre. The damage the two men were liable for was calculated at some 6,840 square metres, the newspaper said - resulting in a fine of between €8m and €40m.
A lawyer for one of the students told the newspaper that any sentence should be meaningful and have a point.
"What is the sense to impose an administrative sanction... already knowing that the two boys, still students, cannot pay it?" she said.
However, the prosecutor told local news outlet Il Giorno Como that the fine was "a signal that we need to push people to greater responsibility in protecting the environment".
Italian media reports also suggest that the pair could be held liable in separate actions by property owners who were affected by the fire.