This is what always confuse me, why do you need those costume packs. As long as people will pay, then they will release them. If there is a demand then someone will sell it to you. Why do gamers believe everything should be for free. The people that make your entertainment do not work for free.
I work as a developer but not for video games. In the industry that I work for customers are always looking for us to do work for free. The problem is that when you work billable hours, you cannot just do stuff for free. A business has metrics that has to be met by each individual head and if those people are not pulling weight, then they get laid off. This is why you see a lot of developers and other staff get laid off after completing projects under game development studios. Game studios cannot support those extra personnel if they are not working and bringing income to the business.
There is a line that is met between a finish game and DLC. The main game should be finished with a complete roster. 18 Characters look like a complete roster and from what I have seen from the main game, there are a decent list of costume for each character. If the main game is complete then anything else created is done to keep the game alive but also keep those people who are not working on a new project employed.
I didn't need them. I wanted them. I wanted the "complete experience". When it became too much, I quit. No harm done.
Also, I didn't want anything for free. There was just so much dlc that it began to eclipse the cost of the game. Same with DoA, now. When I bought the first game on PS1, tons of costumes was a selling point. Now, the game seems secondary to the bonus stuff. Sign of the times, I guess. But they have a choice and I have a choice. I choose not to support this at all.