I'm finding the talk about making breakfast at home cheaper largely irrelevant.
Firstly, although it may not have been explicitly stated, the OP seemed to be referring to buying a set breakfast from a cafe, pub or restaurant and what a fair or value price would be to different people.
Secondly, it strikes me that culturally, we are still not a nation who make a big thing about going out for breakfast. I'm not saying this isn't shifting as more and more places seem to be adding it to their range, places like Toby, Harvester and Beefeater do them even though they are all known for other things.
The wider point for me is that I wonder how many people plan eating breakfast out in advance where considering buying ingredients instead even becomes a consideration?
I find that on the occasions I have eaten breakfast out, it's usually because I am already away from home, either because I have stayed away somewhere or simply because I am out and about. It's usually just down out of necessity rather than it being planned in advance. Thus I find all this talk of buying ingredients to cook my own totally pointless as usually it isn't an either/or situation.