On the other hand, the discussion delays boarding, you need better/more gate staff, you need the infrastructure to pay out, quickly book to other flights, etc.

On the other hand, the discussion delays boarding, you need better/more gate staff, you need the infrastructure to pay out, quickly book to other flights, etc. I think Ryanair's approach of not overbooking is sensible as it keeps the operation very easy. Also, they can book every flight to 100%. If you deny boarding, you need to offer alternatives. That's not possible if you're the only airline flying from the airport (Ryanair used to use a lot of regional airports) and your next flights are already at 100%.