Ours have left private education now, but ours were:
Choosing to limit our family to 2 children
Me working full time from mat leave onwards even though we could afford for me to be a SAHM or part time worker if we weren't to send children private
No overseas holidays during the private school years, and only cheap UK ones (camping etc) where as we could have afforded multiple luxury overseas holidays if we hadn't sent our children private.
Drove one old car (20+years) where as we could have afforded 2 new cars if we hadn't have sent our children private
Lived in our modest 2.5 bedroom house with a poky kitchen when without school fees we could easily have afforded to buy a 4+ bedroom house.
No updgrading 20+ year old kitchen/bathroom/windows, where as we would have easily afforded this if we hadn't sent our children private.
No big days out or meals out, which would have easily been affordable if we weren't paying school fees
DH and I buying minimal replacement clothes/using charity shops and car boots etc, generally having to penny pinch where wwe could.
We were earning £150k+ and living a pretty frugal lifestyle - that's the sacrifice.
I'm well aware that many, even without school fees are only living a frugal lifestyle because that's all their salaries will stretch to. But we were earning well, so the difference between how we could have afforded to live without school fees and how we actually lived with school fees was the sacrifice, and yes, I think it was a pretty big one. We went without a lot of things we could otherwise afford because of the school fees. We didn't go without basics, but we went without lots of luxuries that other people at our salary level take for granted.
I must admit, now they've left and are at Uni, I'm loving the fact that we feel positively loaded even though we're topping two children up fully. I've loved being able to extend the house, buy a new car, go on holiday, go out for dinner on a whim etc. I think I appreciate it more though for not always having had it. And there's also the unintended consequence that we're better off than we would have been because both of us working means we've both had promotions and payrises, both paid into pensions etc, so the future looks pretty rosy for us.
I don't regret it at all though, and am happy with our choices.