When I am instructing one-on-one I do charge a higher rate than for group based sessions/classes.
You can understand the difference & challenges between the two. Group sessions offer more participation @ a lower investment and sometimes more “group” support.
Personal Training/Coaching for me is more direct. I have to focus on programming, motivating & educating the one, not many. It is just as draining as both afford my direct attention/energy. For some this can be more challenging than with “generalized programming” usually used in a group format.
Group should offer more “group motivation/support.” That is the real benefit, not the $, (just my opinion).