There is a new Pentax K1 ($1,896.95) vs. Nikon D850 ($3,296.95) image sensor quality test comparison video:
https://www.youtube.com/watch?v=ngjFgTQW1Ik
Related videos:
https://www.youtube.com/watch?v=xtWxv2X22qM
https://www.youtube.com/watch?v=1jualEjBvPU