I'm still at about 11 cents/rd for 55gr 223 SP. This is with LC brass, Hornady 55gr SP, Wolf Primers and WC844 powder. As my supplies deplete this cost will increase. I'm still loading from components purchased 10+ years ago.
I’m currently at about 5 cents a round because I got a 55 gal drum of once fired brass for $20 and the components I got for dirt cheap as a local gun Shop when bankrupt and liquidated their assets for pennies in the dollar.
But this was just a case of being in the right place at the he right time.
Pre-panic, 18-22 CPR. Now, not even possible. You would be lucky to find any decent amount of projectiles or primers all assuming you are using your own once fired brass. For almost 2 decades fmj bullets for the 223 were still about 8 cents each. I doubt you will find any for less than 12 cents per round. Primers were a penny a piece before Y2K maybe 1.5. Here lately 4 cents each is the new normal. If/when you can find them . It seems powder is the only thing still available and it's gone up from $8/lb(serious bulk buying) to $22/lb. even in 8 lb jugs.
So all told it's gone from 20 CPR to 30 based on todays prices. Much more if you get away from bulk bought fmj bullets
I've NEVER loaded a single round of .22-250 (I'm a devotee of both the .250 & .300 SAV cartridges) & see LITTLE reason to load any, as I have rifles in the 2 "old-school" Savage calibers & am pleased with both. = The .250-3000 SAV will do almost anything that the .22-250 will do AND "bucks the wind" better.
I would GUESS that I can reload 5.56NATO for about 15 cents per round (Truthfully, I've NOT tried to figure out a "per round cost" as the 5.56mm cartridge uses LITTLE powder. = An 8 pound jug of powder will load a GREAT NUMBER of 5.56mm rounds.), as I get all the 5.56 "once fired" brass that I will ever need FREE from the same Garand match shooter who gives me his M2 brass.
(He does NOT reload & the "last load" of cases that I picked-up from him was over 1000 Lake City M2 cases.)
Note: Aside from the fact that Lake City brass is good quality, it does not have a caliber on the case head. = I use it to fireform 9.3x62mm.
223 can be reloaded very cheaply, if you buy in bulk. But this only applies to "normal" times, as in not right before a presidential election or worldwide pandemic . In those situations, nothing can be reloaded "cheaply."