I pay 13.75 for 50 lbs Premium Black Oil Sunflower Seed at the mill I go to.
But it is better that the stuff TSC sell around here. I got a bag from TSC about a year or so ago and it was so dry it wasn't funny.
Price in my area varies from $18.00 - $25.00 for 50 lbs. Right now it is on sale for $18.99 but I don't need to buy any at this time. The price seems to go up latter in the winter and spring. I grew BOSS in my garden this year for the birds. I planted lots, I believe it was 5 rows with each being 20 feet long. For the last few weeks, and hopefully at least a couple of more weeks, I have been picking several seed heads every 2 - 3 days and putting them in the run. I give them the head and about 2 feet of stem with leaves. They eat the leaves when the seeds are gone. The birds now know when they see me walking towards the garden with my clippers that they are about to get their favorite treat.
This is the second year I grew it for them. I will grow it again next year. This year I intended to plant 2 rows, wait 2 weeks to plant 2 more rows, and the wait 2 more weeks to plant the final 2 rows. Due t a very cold and wet spring most of the seed from the first planting rotted. The ground was two wet for the second planting. When it was time for the third planting I planted the last three rows at the same time and replanted part of the first two rows. Decided to skip one row because quite a bit would end up getting eaten by the wild birds if the chickens could not eat it fast enough. As I feared, most if it came on at one time. Looked really nice when it was blooming (I have to get some photos next year...). The wild birds have eaten about half of the seeds in each head that have not been harvested yet.