I'm yet to spend over what probably converts to about $150USD on a tree (I'm in Australia); but i'd be okay spending up to $1000 (so probably about $650USD without looking at the current forex rate) for something I really love.
The things stopping me doing that are 1. that it still doesn't seem you often find anything overly good for that sort of money here and 2. I'm relatively new to bonsai and I'm very conscious that I 'don't know what I don't know' (although sometimes I feel I do) in terms of my maturing (hopefully) tastes alongside experience and so forth.
I'm someone who really aspires to develop some trees that are my own and enjoy/learn through the process, but it'd also be nice to have something good in my collection; in saying that, I want to set aside thing to look forward to ie. spending a little more on more advanced trees as I myself, progresses.
But yeh, moral of the story, for $1000AU here, it's seems difficult to get anything great (in my limited experience). You can certainly buy a decent trunk, even some decent primaries, but it doesn't seem like you're going to find much beyond that.
(I really hope I'm being ignorant here and just haven't found the right sources - maybe someone more travelled can set me straight if so).