The cost is mostly in the labor; not the materials. Plus, there is overhead of owning a shop, etc. I used a generic, premade Bimini on my Pearson 30 for a few years. White only available. Installed it myself but it did not go past the backstay. No modifications. Back then in 1993-‘95 it cost a couple of hundred dollars. When the first one started to look shabby, I just got another one to replace. Eventually, however, I did have a custom one made.