You ask if they are worth buying, then follow up by stating that you remember seeing and enjoying them back in the 70's.
Mark Wilson was/is an American TV pioneer. He was instrumental in staging magic for television, and for years he was the face of magic for many of us.
The shows are a study of a time gone by. You will see how Mark and his creative team began adapting illusions to look good on the tv screen as opposed to the theatre stage. He was no Doug Henning or David Copperfield in terms of theme, dance, etc., but instead embodied the classic magician's look of the time.
If you enjoyed Mark's past performances, then you will enjoy reliving these old shows! ;)