Yes, EU enlargement is good for economics and budgets, because the group will have more influence the more members they have. The European Union will not be a susceptible to sways in economies of single countries. They will have a larger budget to work with. Their opinion will have more sway in international affairs.
The expansion of the EU, and as such its markets, is good for the economy, because it means more people and more markets to enter, and a stronger European market over all. It is all good for peace and good for integration of people, so it's fulfilling its purpose quite well.