Your question seems to conflate open access with APC, which is a mistake.
1. There are Gold OA journal without APC (at least in some fields, including mine, mathematics).
2. There are many green OA journals, i.e. journals that let you post the "postprint" (author's layout of the post-peer review version) of the article. Many publishers, including big commercial ones, have this policy. The journal version is still beihind a paywall, but the science is still open (and I tend to prefer my layout to the journal one in many cases).
3. There are OA journal where you have to pay, but very little: PeerJ (also has a computer science version) asks for 100 to 300 bucks for a lifetime worth of publishing; journals run with Scholastica ask for 10$ per submission (sometimes paid by the institution funding the journal).