Namco has trotted out yet another couple of Namco Museum releases for $19.99 each on PSN. I'm asusmin gthey are out on other systems as well.
Volume 1
Galaxian, Pac-Man, Xevious, Mappy, Dig Dug, The Tower of Druaga, Sky Kid, Dragon Buster, Dragon Spirit: The New Legend, Splatterhouse: Wanpaku Graffiti, and Pac-Man Championship Edition
Volume 2
Galaga, Battle City, Pac-Land, Dig Dug II, Super Xevious, Mappy-Land, Legacy of the Wizard, Rolling Thunder, Dragon Buster II, Mendel Palace, and Gaplus
There are regular and 8-bit "demastered" versions for Gaplus and Pac Man CE.
If these were all on one for $20 and it included the arcade version of Splatterhouse, I might bite. $40 for 20 retro games that have already been released dozens of times (including some on PS4) is way too much IMO.