Yeah, I just talked to him again myself and thought that was a bit steep as well. Don't know what else to suggest. In my gallery pics, near the end are some shots of my buddy's '83 cuddy with an enclosure he made himself. He started with a standard Bimini top and purchased the Eisenglass PVC from Saftler's Fabric Shop here in Whitman, MA. Matter of fact, he bought all the supplies from them including snaps, edging material, they even let him borrow the snap tool to install them with. All said and done, he spent around $550 including the Bimini with supports.
The only thing I would have done a bit different would have been to use a Bimini just a bit shorter in length. You have to be aware of it when casting.