If you're comfortable with Diamond brands (and I believe Pro Plan has had a recall for salmonella in the past so not much difference in that regard), a lot of Diamond foods are pretty good. Diamond Naturals is very inexpensive ($28.99 for 40 pounds at the TSC here), but has a named meat meal as the first ingredient, no artificial colors or added sugar, and no meat by-products. 4Health (TSC's store brand) is comparable in quality and usually costs $29.99 for 35 pounds. Chicken Soup for the Dog Lover's Soul (and, yeah, the name is terrible) is a step up (I pay $32.99 for 35 pounds). If you have a Merrick supplier in the area or are willing to buy off Amazon, Whole Earth Farms is about the same quality and costs about the same.
Those are all the decent foods I can think of in the $1.00-$1.25 a pound range.