I switched from the Tab S7+ to the Tab S9 Ultra for $499 with the trade-in in October 2023. I was really excited about the IP ratings on the Tab S9 series. The thing that killed me was that I had to buy a new Book Cover Keyboard for $350.
When I got the Tab S7+ somehow I got the Book Cover Keyboard for only $99. I know that they gave them away for free with the preorders, and maybe with the Tab S8 series too, but then with the Tab S9 series I think they only gave away the Book Cover (no keyboard). I wasn't going to get the Tab S9 series, or upgrade to the Ultra, but the trade in was great. I also wanted the IP rating for water resistance. I was a little scared to go bigger, but I have loved having this big display. The + line is still a good size too, but I feel like any smaller, and I could just use my Galaxy S23 Ultra - that's a pretty big screen.
Occasionally I use the Tab S9 Ultra as a second screen with my laptop, and the screen is actually a little larger than my laptop. It makes for a great setup when I can't be docked and connected to my dual monitor setup at my desk.