I've read around 10 percent shrinkage should be expected but my experience is significantly more, closer to your 20 to 25 percent. If you start with skin-on belly, I'm guessing that is another 10 percent loss in terms of bacon weight (but a big gain in the Chicharrón category). At least they tell you to reduce the cure by 10 percent of the meat weight if you are curing pork belly with skin on in the government food manual.
I lose even more because I do a warm (150F internal) finish to my bacon so I'm utterly convinced it is okay, really really okay. My wife shares it with her friends and some of the guys in my social set are pushing seventy. So I really want to be sure I am not giving them any buggies. While it may not be necessary, it reassures them to know its been brought to a "safe" temp when being made. (Yeah yeah, I hear all you cold smokers out there!) But that costs me some bacon grease, which is a something of a heart breaker for me. I cook my bacon in the oven so I can catch all the bacon grease for my other culinary adventures. I hate losing it in the making, but so it goes.
The flavor of homemade, smoked bacon is what it is all about. You just don't walk into the grocery store and get that in packaged stuff. If I lost 50 percent weight, I'd still be making it!