I haven't bought any in a long, long time but if they still make it the same, it's good stuff.
That price seems really high though. I just looked at the G&B site and for some reason their 4x price is the highest price of all the panels. I wonder why?
I don't know if money is an issue for you but they might have a huge used section. There are so many retail shops going out of business that I imagine fixture stores are packed with used things. You can find them on craigslist too (look for retail display fixtures).
If you need odd things it can be a good idea to build a relationship with a supplier, though. I would go in and say "I need a thing that does this kind of thing" and they'd help me construct it. We'd go back and dig through stuff looking for odd parts, reinventing the wheel. It was so much fun.