Usually 30–50% cheaper than physical book.
If you cannot get the PDF, here’s a workaround: Buku Ppkn Kelas 7 Erlangga Pdf
If cost is a constraint, the Indonesian Ministry of Education releases under Kurikulum Merdeka. These are legal PDFs you can download from the Buku Kemdikbud website. While not "Erlangga," they cover the same competencies. Usually 30–50% cheaper than physical book