I’m sorry that happened to you, hopefully OpenAI is understanding and can identify exactly what happened.
I suppose one of the lessons here is to develop safeguards to ensure your assistant can’t go rogue or get stuck in a loop before you take your eyes off of it.
It could have been worse though. While $260 is nothing to sneeze at, I imagine under the right circumstances you could have burned a lot more cash, I’ll share my own tangentially related tale of woe…
Many moons ago I was working for a small startup that was hired to do the backend of a promotional website for Windows ME. Some electronic version of a scratch-off ticket where you could win things like Windows ME T-shirts, hats, other merch, copies of the OS, and even some cash prizes.
Long story short, I pushed the wrong backend version to the live site before going home for the night—the version with substantially higher odds of winning prizes I was using to test all of the assets were loading properly and the page would redirect winners to the proper pages to enter their information.
I got the panicked call around midnight from my boss that we’d apparently awarded on the order of 5x as many prizes as had been allocated for the entire month long promotion in under 3 hours.
It was like a three minute fix to pull the site offline, push the proper version and bring it back up, but it felt like forever.
Walking into work the next day was possibly the scariest thing I’d ever done in my life up to that point.
I was absolutely floored when my boss didn’t fire me or throw me out of window. What he said instead has stayed with me all these years later.
“Why would I fire you? I just paid $60,000 to teach you to never push the wrong thing to production and to never leave the office until you’ve triple-checked everything is running perfectly.”
And he was absolutely right, to this day I remain ever vigilant against the possibility of runaway systems.
So, 
and welcome to the club.