From my magazine (historical) related collection:

[*]20th Annual Anniversary issue of "Playboy"; Jan 1974, $1.50
[*]25th Annual Anniversary issue of "Playboy"; Jan 1979, $3.00
[*]30th Annual Anniversary issue of "Playboy"; Jan 1984, $4.00
[*]35th Annual Anniversary issue of "Playboy"; Jan 1989, $5.00
[*]40th Annual Anniversary issue of "Playboy"; Jan 1994, $5.95
[*]50th Annual Anniversary issue of "Playboy"; Jan 2004, $7.99