The folks at http://www.thundertiger4u.com are now advertising the F-75s for $169.99, and they ship all orders $150 or over for free.

As for where I got the idea that the F-91s came with an air-bleed carburator:

http://www.acehobby.com/ace/TTR9801.htm

"Precision air bleed carburetor makes adjustments simple, and efficient mufflers keep things quiet at the field."

Thunder Tiger and Ace Hobby would do themselves a world of good by updating their website with current, accurate information.