$52? Here are some other sources for less expensive NACA ducts.
Black and Clear. These come with an intergral "exit" tube at the
larger end. Other sources don't have this tube, just an exit slot the
size and shape of the larger end. Google "naca duct".

Try racerpartswholesale dot com which has both black and clear lexan.

Replace "dot" with a period. Google is blocking this post for some
reason when it contains full URL's.

Thanks.