Personally, I won't spend that much, or even half of that on a mix breed... There are plenty of full blooded dogs that are about the same size full grown and cost less... But it's your prerogative....
I met the sister of that breeder one time. She came into the store I work at to buy him little clothes... (he was about 2.5 lbs at that time)
Do what everyou want! Don't let people talk you out of buying a baby you really want if he's healthy and you trust the breeder...