Proline shooters in Calgary has PPU for Somewhere around $24 a box. Best deal I’ve seen and great guys to deal with, don’t know if they ship though.
Cheapest I've seen is around $21-$23/box of the Russian made steel cased LVE .303 (often rebranded as Wolf Performance Ammunition). It can be, okay, depending on how tight of a bore you have. The problem with this .303 though, is that the bullet is a .308, not a proper .312 - which can cause keyholing. For "cheap" .303 it may be worth buying, pulling the undersized bullets and reloading...
It helps to have picked up .303 here and there over the years.
Haven't had any reason to crack this one open yet.
https://flic.kr/p/2ieHxSR https://www.flickr.com/photos/162118399@N03/
Lol, that's sweet.