Yes when I shoot sports (typically just school sports these days but I've done golf, rugby, football, horse racing, running) I'd probably expect 10% of shots to be keepers, and if I get a couple that I'm very pleased with then all the better.
I spend about as much time processing photos as I do taking them, and charge accordingly, and I think the post-processing is at least 50% of the job. In fact, when you're photographing sports, there's just a whole load of luck involved. Yes, you can put yourself in the right place sometimes, but much is blind luck. You still need to know your kit inside out, but that's a given when charging money.
I certainly don't call myself a pro, because I only work for one independent school, but that's enough for me at my age and they keep me plenty busy enough.
Funnily enough (or maybe this is common), I have zero interest in photography as a hobby. Sometimes I'll take a few bird photos in my garden, but that's about it. That's why I very rarely buy kit, because it has to pay for itself (or because I destroyed it), and the school never says my photos aren't good enough (far from it). Last purchase was that 70-200 f/4, and before that a Z6 three years ago. Always second hand from a reputable supplier.
