Since you have this desire since a child, its would be well worth it to pursue. Check any local ranges, you may be surprised as some will actually allow you to rent a full auto.
In order to give an idea of cost, here is your list with an approximate price range:
I believe the TEC9 and MAC10 are more afforable and actually under 2K.
These prices are off the top of my head and are not exact. Monitor the subguns board for a month to get a good indication.
The website provided by chetchat is a great place to start.