Alternatives or cheaper way to access GPT-5 thinking?

I love GPT-5 Thinking, it takes its time but it gets me the best results, even compared to Claude Opus Research for example. But, currently, I have two subscriptions, one to claude for claude code which seems like the best coding agent by far, and one to OpenAI for the GPT-5 thinking chatbot. I wanna get it down to under $20/month. Are there any other alternatives to GPT-5 thinking or just platforms that get me cheaper access to it? I honestly don't really care about image generation or the myriad of other options that OpenAI provides, I just want a low cost reliable alternative that gets me GPT-5 Thinking.