I think it is more of a humanitarian decision rather than an economic decision. Because many of these illegal immigrants are given sub-human treatment in farms and other work places. They don't get any public welfare assistance. Sometimes, we can be happy that there are laws being made which will make people treat humans likes humans.
I don't know why you get disheartened about other people getting a chance to live like humans. You didn't have to live in fear of deportation for 7 years. You were not treated sub-humanly. Does that freedom count for nothing?
Moreover, as Obama is taking executive action, the next president can take back this decision, when you don't have to worry about anything, but these people do.