The cost of crewing that flight would be high, but then the cost of parking it up for the day is also high both in terms of fees and opportunity cost on the aircraft.
I think the whole Barcelona thing was pre-launch with the idea the flight would be crewed from there, but that doesn’t seem likely now. In terms of opportunity, Alicante seems relatively underserved compared to other holiday airports in Spain and Portugal. There are also possibly opportunities to Seville and Valencia, but neither are served by Norwegian from anywhere yet.