I realise this is an old thread, but I noticed the title, and it struck home with me. I know how you feel.
I have been feeding a low to medium quality black oil sunflower seed in two of my feeders and Safflower Seed, both by Wagners, in one of my feeders. My songbirds love both, and they go through a 25 lb bag of the sunflower seed in a little over a month---I replenish the feeders daily.
The price of the 25 lb. bag of sunflower seed is now well over $40 a bag, and whilst that may not seem expensive to a lot of people, I am a retired senior, and my budget is not as flexible as it was years ago. I have not found a better alternative to the Wagners, though. I used to feed an higher quality seed from the Wild Bird Store until it closed down a few years ago, but I could no longer afford to feed it at the rate my birds eat anyway. Until/unless the price drops on the seed, I am going to have to feed them less each day than I normally would do. You might try the Wagners, but be prepared for the clean up as the Wagner's seed is not hulled, and the hulls go everywhere.