Nope, custom framing is expensive. Especially if you have chosen multiple or specialty matting. Glass also adds to the expense.
My sister sent me a signed/numbered pointelle painting from Africa of a Rhinoceros. It is an 8x10. It cost $150 to frame. I, too; almost fell over when I ordered, but because the piece is more valuable, I went with it. A good chunk of that cost included glass that blocked UV rays and was anti glare. And that was over 15 years ago.
The piece you are framing is quite large. You have to take that into consideration. It also takes time and labor to put that frame together and cut the matts properly and the glass if you are using it.
You might try an actual framing shop. They may or may not be cheaper