I've priced to the cost per pellet and added in shipping (very anal about getting the best financial deal). AoA would be the best price, except their shipping is twice everyone else. Even with the shipping, they barely nudge AGD and Pyramyd, but were out of the .25 Kings last time I tried to order. AoA does buy 4 get 5.
Next best was AGD, even including shipping. PA was within a buck or two on the whole order. Both do buy 3 get 4.
UAG was next and only a couple bucks per order different. I believe they do the buy 4 got 5, and are a bit cheaper on per tin price.
I shy away from Amazon as pellets are usually an "Add On" item meaning you must buy $25 of something else to get Prime shipping. Last pellets I bought from Amazon were in a box with absolutely no packaging. You can guess the rest.
PA and AGD pack absolutely perfectly with custom packaging materials. Never had a problem there.
Haven't tried other places, I'm sure some pack extremely well too!