What you are missing is the fact that, if this were a time BEFORE DLC existed, do you really believe those 12 extra characters would have been part of the game? The more likely answer is absolutely not, they wouldn't even have bothered with them. The only reason they were worked on in the first place, is because they KNOW DLC exists and is a viable opportunity to provide extra content for extra money. So its not like they said, "hey we are done with the game, lets lock down a few characters so we can sell them at a later date." It is more likely that they said, "hey, here is some extra development money so you can work on some extra characters that we can use for DLC."
I'm not saying this is definitely what happened, but I'm explaining a likely scenerio that developers go through nowadays because DLC is a viable option that is known about before development even begins. So it isn't that content is being taken away because they know they can get more money from you later, its that that content is only being worked on in the first place because they know they can get more money from you later.