Presumably it's scrub land because nothing's been done with it for years? So it could possibly still grow good grass or whatever, if properly cultivated.
Essentially it's worth what it's worth. How often does land come up for sale near your house? Is it a plot that you would particularly like to have to add to your smallholding? If so, then it's worth more to you than just its theoretical value as a piece of "scrub" land.
I recently bought some "scrub" land at auction. It was full of gorse bushes. I paid twice the guide price because I wanted it. It cost a lot more to clear it, seed it and fence it. But it has proved invaluable and well worth the money. So really only you can decide.