I usually only buy ammo when I first use a rifle. One less variable in case the thing goes boom in a bad way. After I'm comfortable with how the rifle is functioning, I'll start working up my own loads.
Just quick off the top of my head to reload the 7mm-08...this will be very similar to cartridges like the 308 Win, '06 based cartridges, etc... Larger cases like your Weatherby Mag will use more powder, which will add a few cents.
140gr Nosler Ballistic Tip = $0.44
Primer = $0.03
Powder = $0.11
Brass = $0.05 (assume multiple uses, brings cost way down)
That's $0.63 per round. Reloading centerfire brass is very much worth it. For plinking, you can get even lower on bullet cost.