If that's a price for a good ground glass that you know will fit, it's a good price. Don't sweat it.
I have replaced two broken ground glasses. The first one was for a 4x5 press camera -- I made my own with glass I cut from a picture frame, and grinding compound. It worked fine, but took half a day to get the needed items and to grind to spec. Total cost was probably $25. The second was is for my Graflex Graphic View II. I bought a new-old-stock ground glass from the local camera shop (I think for a Linhof) and cut it to fit. Cost was probably $40.
So if you can buy a ground glass that fits and is ready to go, at that price, just do it.