This was the fare shown on ba.com for a Thu - Mon return trip on a over the second weekend in April.
I'm not asking if they're better than Ryanair, I'm certain they are. But Ryanair are charging £140 return for similarly timed flights with 20kg bags and emergency exit row seats on the same day. Are they £400 better than Ryanair?
The fares do seem rather high - they seem to be priced at £269 per flight, compared to £114 for MAN-BLL. Having flown the latter, I can say Sun Air service is fantastic, much better than BA's. Onboard service includes a meal (fairly decent ham & salad roll IIRC), followed by ice cream & baileys, as well as a pre-meal drink. Good service, but probably not £400 worth.
(Tip: don't ever go to Billund for the weekend - there's only one pub, and it doesn't open until 10pm!)