My cost per round calc is pretty simple: it’s cheaper, it’s more accessible, accurate ammo that shoots well is more reliably available, I can have multiple ammo types for the same firearm and not have to wait/search/travel for it.
Plus, everything costs 40 bucks so budgeting debates with the wife are a non-issue… 
Depending what you’re shooting, postage is going to eat into your costs pretty heavily, as is actually having somewhere to advertise your brass - especially now Facebook fucks people and groups up for selling it there, and you can’t use eBay either.
Heh, I do this when it comes to car parts.
“You see honey, by fitting the larger turbocharger the engine doesnt have to work as hard making it more efficient. I beg your pardon? What do you mean bigger injectors use more fuel? That’s crazy talk, all good cars have 2000cc injectors for safety.”
For hunting rounds, I calculate the brass on the first shot because even the big banger shells disappear in the grass. Every reload after that is a bonus.
I find that keeping the cost of my expenditure is not good, first if the cook found out then, well we all know what comes next. Second sometimes it scares me and It might (not really) make me stop.
Yes mate I tend to pick the price tags off the myriad of projectile boxes I have on my reloading bench. Literally thousands of dollars worth there, not to mention powder and brass etc. I am certain she would be horrified if she knew how much I had invested in my “hobby”.
We need to stop this conversation vector or all of us will be dead lol
416 Ruger
(New 20 pack of factory ammo, $135)
New unprimed case $2.50
Woodleigh 340g weldcore $1.40
82g of AR2208 $0.46
Primer $0.09
Yeah I really need to pay more attention to ejected cases.