I joined the GPT4 waitlist 2 or 3 days after it was released (around mid-march) and finally got access last week. I also applied for personal use and wrote one or two sentences about wanting to experiment / compare it to other models. So they definitely do give the API access to regular folks as well, no idea how they prioritize it though. I've been a paying customer of ChatGPT plus for three months now which might have helped.