Gitlab enters the room, where self-hosted runners are as free as in free beer (maintenance yes, but no limit on runners and no pricing expect on a per-user basis).
Yes, gitlab does still have free self-hosted runners. OTOH, github has a free organisation plan and gitlab doesn't. So yes, strictly speaking self-hosted runners are free, but you're paying for the dev-seats.
Yet.
Gitlab has proven in the past perfectly happy to hike prices above GitHub, after attracting enough switchers.