According to what I've been able to find: A cheapish restaurant meal, a medium-to-nice bottle of wine, a taxi ride, or a cinema ticket. http://www.numbeo.com/cost-of-living/country_result.jsp?country=Sweden
An english-related question: is the translation “crown” commonly used? I know that in french you use quite exclusively the translation « couronne » for thrice swedish, danish and norwegian “crowns” (and certainly others that I don't know of), but seeing it by default untranslated on Duolingo (though “crown” seems always accepted) make me doubt about english.
I would say "Krona" is more common. It's hardly scientific, but "Swedish krona" has about 22 million hits on Google to less than a million for "Swedish crowns". The results on the search page for "crowns" is generally all to pages that are titled "Krona" , until you get down to the coat of arms. That said, I think English ears tend to think krona as plural- I've never heard anyone say "kronas", let alone "kronor". If anything, I would not be surprised to hear someone refer to one krona as "one krone".
I use "kroner" as the plural for "krona", although I don't recall where I picked up either "krona" or "kroner". For sure it was before I started this course. "kroner" isn't accepted here, although (I think?) it would be valid if this were a course in Norwegian or Danish.