I think I'm the closest to being officially sponsored. I'm a Google engineer that spends my 20% time working on babel, and my direct team donates $100 on top of that.
@hzoo is a Behance engineer, and I think he spends roughly 50% of his time on babel?
Other than that, we're all unpaid volunteers. There's some backers on opencollective.com/babel, but not nearly enough to sponsor a full time engineer.