Welcome Chris1948 from yet another 1948 fan.
Interesting Greenhouses and prices. Love that Angel Trumpet. In Hawaii everything is "plus shipping" which increases our cost. I buy the Costco Car Canopies with heavy metal tubular frame for $269. I then sell the cover for $110 (lots of folks have covers that wear out) and then my frame cost is $159. Just have to buy the plastic cover to throw over the 10 x 20 frame. In Hawaii we don't have to worry about closing the ends. I use a greenhouse to protect plants from excessive rain which can reach 150 inches a year in our area.