With the increases in feed costs over the last couple of years, I am sure you have more than $25 into your bird. However, it is often difficult to recoup costs when selling live birds. Kind of weird, especially when selling a young bird with a lot of breeding potential. Market value is what market value is, however. It would not be out of line to make a counter offer. You may have upwards of $50 into a 7 month old standard bronze, just accounting for feed (if it is 30 lbs, its probably eaten about 150 lbs of feed assuming a 5:1 conversion for heritage turkeys). You would certainly be on solid ground to estimate your feed costs and ask at least that much. You may not get it, but you can ask!
From the buyers perspective, if I was looking for an adult turkey, and found one for $25, I'd snatch it up as a real bargain. So I think you could probably get a little more for it.