Plain and simple, it really is expectations. The “cheap” birdseed blends are filled with fillers like milo, cracked corn, wheat, sticks, stems, rocks and who knows what else. If he is OK with feeding hordes of House Sparrows, grackle and Mourning Doves then the cheap mixes are probably fine. If he wants to attract cardinals, chickadees, flickers and other beautiful birds then he will do far better with quality seed. A 50lb bag of Black Oil Sunflower (the favorite seed of more birds than any other) is (check for current price). I can’t imagine a bag of the “cheep” seed costing much less.