Sharpening on the mill is in no way a fair comparison. That would be like saying that I can sharpen a $200 14" carbide ATB saw blade on the saw just as effectively with a dremel tool and a diamond bit from home depot as compared to a professional sharpening service with a computerized sharpener. Its simply not possible.
Can I sit at a TV tray in front of the television at night while Im munching on some cheetos and "re-touch" a blade with a dremel? Sure can. But its in no way the same as having the blade professionally sharpened.
There is one immutable fact. When people do things themselves, build their own gadgets and gee gaws, they make great accommodations (excuses) for the short comings of their end product. We all do it. They can often live in a world of delusion thinking that they saved a fortune, or that it didnt really cost them anything because they had this stuff laying around, or it really doesnt matter because "all that was just scraps anyway". All the while it cost them ten fold in time and energy and they worked for pennies on the dollar for something that will require endless tending and tweaking and live a very short life.
Its still good work but the simple fact is, you can not build a truck for what you can buy one for right?. To think you could, and be profitable, would require you to lie to yourself about the countless hours, trips to the store, fuel, time, research, ancillary equipment, and so on, that we conveniently leave out of the mathematics of what it actually cost. Not to mention that the truck would require endless repairs, be broken down, need to be tweaked, would only be able to be driven by one driver who knows all the problems and work arounds, and so on. "oh, dont look at that, you gotta pull this lever, shove over here, hit this with a hammer, then it'll start".
Its not to say its a waste of time but when it comes time to compete on the open market, and your forced to compete apples for apples, it gets far more difficult.
It would be like you selling your oak shingles. In the time it takes you to shove your screwdriver wedge in to tilt the cant, a shingle mill has made a dozen shingles or more. Forget about the issues of red oak vs. cedar (I know some were chestnut oak which would have been a wiser choice for them all).
The point is whether or not you will think your red oak shingles are #1 viable, and #2 that you can make them _cheaper_ than a shingle mill because they are made from scrap or whatever. The simple fact is you cant. They need to be marketed to a clientele who want shingles made one at a time and are willing to pay 5-10 times the cost of anything available on the commercial market because thats what it will cost you to make them.
As always, Im not trying to poo poo your work ethic or enthusiasm.
Same thing as always, when you add up all your time and expenses honestly (without lying to yourself) it will often work out to be far less savings than you want to believe.