As strange as it sounds when it comes to PSP porn titles, it's a seller's market. The reasons behind this is simple. Few titles, limited market back in the day. Plus the fact there were only available in places that sold porn. Even then places that cared to sell such a unique item. Take here in the US, we got 2 titles, Casey The Co-ed. I have only ever seen this title listed twice on Ebay , selling for $9 and $90. That is no mistake, 2 prices $80 apart. Although you can get a DVD of Casey for around $10. I know of at least 15 released in Europe. Bouncy and even a teaser video called Dream Models. As for Japan, I hear from collectors that they are fairly easy to find on Japanese sites. But even then they can be expensive. I am uncertain on how many tiles were released in Japan.
Mainly imports, and even then who actually has one. It would be safe to say finding a rare import PSP game is easy to find in comparison . Or that Adults Only content Playboy had available to it's subscribers for the PSP. Although I have heard of some seeing them, no confirmed case of actual ownership. In other words hard to find, and according to collectors not impossible to find.
All I can say is good luck to anyone wishing to start a PSP porn collection.
UPDATE
From other PSP collectors I got an update about Playboy and it's PSP content
No mystery, they did one promotional release for their paid service with the contents you mentioned (all of them SFW), and everything behind the paywall was just a downscaled version of the normal online content.
