My largest plate camera is a 12 x 15 inch Vageeswari with book plate holders. That is as large as I have been able to buy. A '12x20 Century' on Ebay didn't sell for 800. Was it a plate camera? I don't know.
How big did plate cameras for dry plates get?
There is a photograph called "Kinsey and his Cameras" circa 1910 of which I purchased a hand printed copy. It shows him standing in front of his old car and many cameras all set up. One is looking like a book plate holder about 20 x 24. The holder is almost as tall as the tire on the car! The camera above it doesn't look to be large enough to hold it but is still very large - so large that it requires two tripods to hold it.
If there was a larger plate camera on the market I'd need to add a room to my house let alone the darkroom in order to house and use it. Just curious.