I think you misunderstand one thing. The cell data is on demand, not a monthly fee. If I used it twice a year I’d pay $40.
With the first iPad I went with the idea that wifi is accessible most places. It turned out not to really be true. At school events and other kid extracurricular activities where I’d be sitting around for long periods there was rarely any open wifi.
I don’t go places to use the iPad. I use the iPad sometimes when I go places. There’s a difference.