Shameless plug: I run https://tefter.io a pinboard alternative which supports importing your bookmarks from pinboard and even has team collaboration features.
No shame in that, since your service is even cheaper. Oh. Nevermind. /s
(In perspectice for 39$/month I can self host 1+ premium vps server(s) and run one or more of those https://github.com/awesome-selfhosted/awesome-selfhosted#boo...)
I have an even cheaper service for you, an open-source self-hosted bookmarking service (Espial) that can import from pinboard export files.