The 90000 series is tiny. It's physically the same size as the normal slim but has an internal power supply. If Sony had used an external power supply they could have made that thing the size of a portable CD player.PS2 had some of the most amazing cost reductions ever.
It became the size of a DVD case in its FINAL FORM!
The PS3 and PS4 barely got anything that can be called slim. And they were/are sold at considerably high price compared to older generations