Actually a legitimate concern, because having one team be unbeatable forever is bad for interest and marketing in areas that aren't that team's home market. It's why some of the big national leagues have salary caps (per player or per team) or other means of restricting trades/drafts/hires so a successful team or one with an owner that is willing to sink their own money into funding it can't just outbid everybody else to get all the best players on one side.