Yes, there is one for each member and there is a box set packaging all four together.
As for whether or not they are worth it, not for that price in my opinion. They are independently released interviews from 1977, and while nice to have, not worth $20 a pop.
I got the Freddie disk from this set years ago but never ran accross the others at any store or sale. I am hopeing to get these all someday. The most interesting part I think is that while these are four seperate interviews of each member, they were all done after the same show in 77. It would be nice to hear each ones different opinions and views from the same time period.