I am afraid to add up my fixture, but I'm thinking around $1500-2000. I'm not very organized so finding all the receipts would be brutal. That includes some tools like a solder station and other odd balls. It adds up quick and I even had some freebies, like the aluminum housing. But I also took months to build mine. The hole tapping alone took 12 hours straight.
Like Hoppy said, the quote is really quite good when you consider that you will have about the same functionality as I do but the assembly time will be a fraction of what mine was. I don't believe everyone has the know-how or trade skills to do what I did, but the kits make it much simpler. It's a decent price for a one stop shop.
You could also do something like two radions, one over each hole in the brace, but you have to be willing to deal with the uneven lighting. You may have to shine whatever light use use through the bracing and deal with the outcome. It's going to be hard to have even lighting through only the open areas of the brace.