I’m also interested. Just took a look at the website for the ferry mentioned above.
It seems he means it won’t leave unless there’s at least 400 people. It doesn’t start it’s service to the islands until July 4th (actually it says Monday but 4/7 is a Wednesday??) and leaves and returns once a week for an estimated 10 trips.
Looks like the only return service is the same day so you have the choice of staying half a day, staying a week or flying back - although actually I’m not sure you can even do that; the tickets might just be for the same day return. Doesn’t look like you can buy a one way ticket
Return ticket costs 7500NTD return, minus 1000 if you buy before 8th June. I think you can bring a bicycle on for free. There’s also 2 different tour options for 3500/4000 (meals, tour guide, stuff like that).
Boat arrives midday and leaves 7:30pm
Those are the main things I could gather. It looks like you’d spend half as much as you would flying but if you can indeed only stay 7 hours then it kinda blows in my opinion.