Even if the alternative is free, how much do you value your time, how long will it take to set up an alternative, and how much use will you get out of it? If you're getting less than a million tokens and it takes half an hour longer to set up, you'd better be a student with zero literally income because that cost of time matches the UN abject poverty level. This is also why it's never been the year of linux on the desktop, and why most businesses still don't use Libre Office and GIMP.
I can't speak for quality; even if I used that API directly, this whole area is changing too fast to really keep up.
Most of the other options just work with the transformers library.
And from my personal experience Ada embeddings are not the best. They are large (makes aproximate searching harder), are distributed weirdly, and zimply put, other embeddings give better results for retrieval.
Another advantage is that you are not an OA's whim: they just announced the deprecation of some previous model. What are you going to do when they will deprecate Ada v2 and you've built a huge system on top of it? You'll have to regenerate embeddings and hope everything still works just as well.
https://huggingface.co/spaces/mteb/leaderboard
Of course, that's far from saying that they're the worst, or even headed that way. Just not the best (those would be a couple of fully opensource models, including those of the Instructor family, which we use at my workplace).