Importing is not all that expensive:government forms are around $125 if I remember correctly.
The hassel is that you have to have a vet on the other end that will sign off on the papers. However, if you are coming from somewhere like the UK then that is not a big deal either.
The cost to ship will be the largest expense and that is possibly something like $250 for a young trio.
So, overall you'd be looking at maybe $500 for a breeding trio, if that. Since the paperwork is the same whether we are talking 1 bird or 30 birds: the major cost is the shipping.
Other than the cost, the biggest deal is going to be the hassel of the whole thing.