I have broke with my playing cues thousands and thousands of times with no problem.
Break cues costing hundreds of dollars are a gimmick.
Good for you but you are generalizing and wrong.
It depends on the power you put on the break, your stroke, the tip used and the shaft itself.
If you soft break and the power that you put into it is not higher than the average power you used while playing and you are probably going to be OK.
BUT....
Some shafts will warp over time when breaking if pushed to the cloth and bend (Mike Sigel style).
Modern ferrules that are soft and light (to reduce deflection) and will crack and break.
The tip will definitely loose shape and will compress and harden.
Carbon fiber shafts that are designed for playing will not survive breaking, the front end is not designed for it and the ferrule/plug will break, the shaft front end walls are thin and will break and split as well.
A decent break cue can be found for $100, don't have to pay hundreds of dollars for one.
A $100 cue is a lot cheaper than replacing or fixing a damage shaft.
If one uses soft to medium layered tips from top brands that goes for $20-$30, breaking with it hard while playing 3-4 hours a week will require changing about every 3 months if you like to keep shape and feel, a $100 cue for breaking will be cheaper in the long run even an $800 cue will be cheaper in the long run.
depending on your stroke, a lighter or heavier cue than your playing cue will generate a better break and more consistent with less effort.
If you are a competing player, you might find your self in a jam and without a playing cue if you use the same cue for breaking unless you carry a few extra shafts that again will cost more than a dedicated break cue, even a solid old school classic maple shaft of a good quality (that won't warp) will cost more than $100.
Heck, for a $100 it could even be a jump-break cue and now you can even jump....
So whatever works for you, is not the general rule and definitely not the rule to follow.