Least expensive is to send them the URL https://www.hpmor.com/ . If you mean a literal copy (of the bits), you could download the site to a cheap USB drive, I guess. EPub and MOBI versions on that site if your friend uses a Kindle or other e-reader. And podcast version if they prefer audiobooks.
If you mean a printed copy, I don’t know of any pre-printed versions. Print-on-demand tends to be quite expensive for one-off. You’re probably best off generating a PDF from the EPub, and having it ring-bound at a copy store.
What’s the least expensive way to acquire a copy of HPMOR as a gift for a friend? Same for Unsong too though lower priority
Least expensive is to send them the URL https://www.hpmor.com/ . If you mean a literal copy (of the bits), you could download the site to a cheap USB drive, I guess. EPub and MOBI versions on that site if your friend uses a Kindle or other e-reader. And podcast version if they prefer audiobooks.
If you mean a printed copy, I don’t know of any pre-printed versions. Print-on-demand tends to be quite expensive for one-off. You’re probably best off generating a PDF from the EPub, and having it ring-bound at a copy store.