In Sweden, travel costs can be up to 166% higher for residents and over 300% higher for businesses than on the mainland.
93% confidence
TransportSweden
Omissions
The claim concerns Sweden's populated islands without a mainland bridge connection, not the whole of Sweden; the figures apply specifically to island residents and businesses relative to comparable mainland municipalities.
The underlying source is the OECD report 'Estimating the cost of insularity', which puts business travel costs at about 323% higher (consistent with the claim's 'over 300%').