Flights in Africa and to/from the Seychelles are usually expensive.
However Air Seychelles takes you on the direct flight from Dar es Salaam (DAR) to Mahe, Seychelles (SEZ) for just $291 RT.
The airline has improved recently since Etihad took a major equity stake.
There are various dates in October and November. Note that the flight is not daily.
The flights are bookable on priceline.com