I have all these attachments and managed to pay only once for each piece. I've never seen that KSMPDX set available anywhere, it was always "sold out" or otherwise unavailable. What I did was get the 3-piece starter set with the roller and the fettucine and spaghetti cutters and this two-piece set with just the lasagnette and capellini cutters.

Amazon is weird for the searching but they are right here:

https://www.amazon.com/KitchenAid-KSMPCA-Cutter-Attachment-Silver/dp/B01ENK4SNC

I'm seeing $116.73 right now but that might just be their variable pricing gizmos.