Here's my 2 cents, well closer to $50. But that's include lights and everything.
I used aluminum flashing from the local home depot. About $20 worth. Pre-painted white on one side, brown on the other. Cut strips, about 4 feet long. Width can be puchased as either 14 or 10 inch. Thin aluminum, very easy to work with.
Bend around and you get cylinders of 14/10 inch height, and pretty much wide as you want. I stacked 3 to get a tube 38 inches tall. Screws for making sections, duct tape for stacking sections.
Used a steel pizza dish with porcelain sockets, on top and you have a light fixture for less than 10$. Pc case fan add for vent. Filter can be placed at the outlet. I'm growing a single nl#5, and the smell outside the tube is undetectable.
I've got a veg going for about 30 days. Work in progress, but it was cheap, and is working well so far. Here's the grow log link.
https://www.rollitup.org/cfl-growing/189475-grow-tube-part-deux.html
