Alsie Express has 11 different prices ranging from the campaign price DKK 399 (~54 EUR) to the last minute tickets costing DKK 1,525 (~206 EUR).
Visit the Alsie Express website to see what's included with the ticket.
Do you want to go to Copenhagen?
Then you can book tickets here:
Do you want to fly via Copenhagen to another destination?
Then you can book tickets for the whole trip here:
Alsie Express has a complete Interline agreement with SAS. This means that you will only need one ticket, and at the SAS website you will be able to book your entire trip from Sønderborg right through to your final destination. In Sønderborg your baggage will also be checked in for your final destination.
If you prefer to continue your trip from Copenhagen Airport with another airline, there are of course a lot of possibilities.
Then you could for example use the Momondo search engine to find your individual trip from Copenhagen Airport:
State Copenhagen as "origin city" and book the trip to Copenhagen separately at Alsie Express' homepage.