The simple fact is that DS9 remained on the air for seven seasons. That is a long run for any television series, let alone a syndicated science fiction series. Paramount is not in the charity business. Had DS9 not been profitable for them, there is no way they would have kept it on the air for seven years. And since then, they have licensed the show to cable television stations, local stations in syndication, Netflix, and have released the whole thing on DVD.
There is simply no question that DS9 has been profitable -- very profitable -- for its owners. The only reason the question is ever asked is because it was never as popular in the ratings as TNG.
But there's no question it has been a moneymaker, and I have no doubt that a remastered Blu-ray release would be profitable for CBS as well. I'm sure they will do it eventually.